Nobel Prize-winning scientist Stephen Hawking dies at 76

Alisa Molotova/Getty Images(CAMBRIDGE, England) -- Stephen Hawking, an award-winning physicist and influential author, died early Wednesday morning, a family spokesman told ABC News. He was 76.

Hawking, whose books included "A Brief History of Time" and "The Universe in a Nutshell," was diagnosed with motor neurone disease in 1962.

The family did not disclose the cause of death, but said he “died peacefully” at his home in Cambridge, England.

"We are deeply saddened that our beloved father passed away today. He was a great scientist and an extraordinary man whose work and legacy will live on for many years," the family said in a statement. "His courage and persistence with his brilliance and humor inspired people across the world. He once said, 'It would not be much of a universe if it wasn't home to the people you love.' We will miss him forever."

Hawking leaves behind his wife, Lucy, and two sons, Robert and Tim. They thanked his fans who have "been by Professor Hawking's side –- and supported him -– throughout his life."

Hawking was considered one of the leading voices in science because of his extensive research and work related to understanding the universe.

He made several major discoveries throughout his career, and once said said his greatest achievement was his discovery that black holes are not entirely black.

"I think my greatest achievement will be my discovery that black holes are not entirely black," he said, adding how that discovery would be critical to “understanding how paradoxes between quantum mechanics and general relativity can be resolved."

In a 2010 interview with ABC's "World New Tonight," Hawking was asked about the best fatherly advice he'd given.

"Here are the most important pieces of advice that I've passed on to my children," he said. "One, remember to look up at the stars and not down at your feet. Two, never give up work. Work gives you meaning and purpose and life is empty without it. Three, if you are lucky enough to find love, remember is it rare and don't throw it away."

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UK seeks allies' support after former Russian spy, daughter poisoned with nerve agent

ABC News(LONDON) -- Britain is weighing its options and rallying support from allies across the West, a day after Prime Minister Theresa May issued an ultimatum saying Russia needed to provide answers to how former double agent Sergei Skripal was poisoned.

Speaking to Parliament Monday, May said authorities believed Skripal and his daughter were attacked with a "military-grade nerve agent, of a type developed by Russia."

The nerve agent is believed to belong to a group of Soviet-era chemicals called "Novichok."

May gave Moscow until midnight on Tuesday to explain how Skripal was attacked, or how it may have lost control of its own nerve agent.

"Should there be no credible response," she said, "we will conclude that this action amounts to an unlawful use of force by the Russian State against the United Kingdom."

Describing the attack on the Skripals as a possible "unlawful use of force" may pave the way for the British government to invoke Article 5 of the NATO treaty, which states that an attack on one member state is an attack on all.

Other options that have been discussed by British parliamentarians and commentators include expelling diplomats and spies from the U.K., suspending the U.K. license of Russian broadcaster Russia Today or a boycott of the 2018 World Cup by the English team or delegation.

The Prime Minister attended a national security meeting chaired by Home Secretary Amber Rudd, the third such high-level meeting since the Skripal incident more than a week ago.

The council will reconvene Wednesday following the expiration of May’s deadline to Moscow, to discuss next steps.

Following renewed interest in the deaths of 14 Russians in London, also the focus of a previous investigation by BuzzFeed News, Rudd said in a letter on Tuesday that the police and MI5 would be looking into the cases to rule out any possible Russian involvement.

"In the weeks to come, I will want to satisfy myself that the allegations are nothing more than that," Rudd said.

Most deaths on the list, which includes prominent criticis of the Kremlin such as Boris Berezovsky and Alexander Perepilichny, were ruled as non-suspicious.

The British have also summoned the Russian Ambassador, Alexander Yakovenko, to the Foreign Office to provide an explanation.

Some allies across the West have responded to May's call. Foreign Secretary Boris Johnson said he had been "encouraged" by the response from diplomatic allies, especially following conversations with French President Emmanuel Macron, German Foreign Minister Sigmar Gabriel and U.S. Secretary of State Rex Tillerson.

Following a phone conversation with Johnson, Tillerson told reporters, "This is a really egregious act. It appears that it clearly came from Russia ... It certainly will trigger a response."

Tillerson added that he did know yet know whether the attack was carried out with the Kremlin’s knowledge.

Leading European diplomat Guy Verhofstadt, who has frequently criticized the U.K. government over its handling of Brexit, also expressed solidarity with Britain.

"We stand shoulder to shoulder with the British people," he said. "It must be made clear that an attack against one E.U. and NATO country is an attack on all of us."

Tuesday morning, the British Ambassador to Russia, Laurie Bristow, was called to the Foreign Ministry, according to local news agencies. At a news conference, the Russian Foreign Minister Sergei Lavrov repeated that Moscow bears no responsibility for the attack, adding that Russia has requested access to the nerve agent that was used to attack the Skripals.

Meanwhile, the Metropolitan Police announced they are investigating the sudden and "unexplained" death of a man who is widely believed by British media to be Nikolai Glushkov, a Russian exile and close friend of the late Boris Berezovsky.

The Met said in a statement that the Counter Terrorism Command is leading the investigation "as a precaution because of associations that the man is believed to have had."

Currently, the statement added, there is no evidence to suggest a link to the Salisbury incident.

The Russian Foreign Ministry appeared to mock the British Prime Minister’s words in Parliament on Monday. On its social media accounts, the Ministry pushed the hashtag "HighlyLikelyRussia" mocking May’s assertion that it was "highly likely" that Russia was responsible for Skripal’s poisoning.

So far, the reaction from Moscow to the British ultimatum has been to denounce the allegations as an invention meant to smear Russia.

There is little sign from officials or state media that the country is prepared to acquiesce to demands that it provide access to its Novichok nerve agent program, or provide the "credible" response explaining how the poison came to be used on the streets in Salisbury.

The former Russian spy, 66, and his daughter Yulia, 33, were found unconscious on a bench in the center of Salisbury on March 4. They are currently being treated in a city hospital and are said to be in critical, but stable condition.

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Nicaraguan police arrest former boyfriend in Binghamton nursing student's death

WABC-TV(BINGHAMTON, N.Y.) -- International authorities have arrested the former boyfriend of 22-year-old Binghamton nursing student Haley Anderson in connection with her murder.

Orlando Tercero, 22, was arrested in Nicaragua Tuesday afternoon and is being transferred to the prison in El Chipote, about 40 miles southwest of Managua, the country's capital, Nicaragua National Police confirmed to ABC News.

Further information regarding Tercero's arrest was not immediately available.

On Friday afternoon, police officers found Anderson's body after they were sent to conduct a wellness check at her home about a mile from the State University of New York, Binghamton, campus, where she was a registered nursing student, authorities said. Her death was ruled a homicide the next day, after an autopsy was performed.

Anderson was last seen alive around 4 a.m. on Thursday and was with her roommates before she went missing, police said. The circumstances surrounding her death have not been revealed.

Investigators initially named Anderson's former boyfriend, also a nursing student at SUNY Binghamton, as a person of interest in her murder, although they did not immediately release his identity. Authorities suspected that he left the country by "international air travel," according to a statement by police.

Police suspected that Tercero chose to fly to Nicaragua because he has family there.

Anderson is originally from Westbury, New York, a town on the western half of Long Island. She lived about a mile away from the SUNY Binghamton campus, officials said, and worked as a barista at a local cafe in Binghamton, according to her LinkedIn profile.

"Our entire university community extends our deepest condolences to Haley’s family and friends, both here in Binghamton and in her hometown of Westbury," the university said in a statement.

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Counter-terror police in London investigating 'unexplained' death of man said to be Russian exile

iStock/Thinkstock(LONDON) -- Counter-terrorism police are investigating an “unexplained” death of a man in his 60s found dead at a residential address in the London area, London police said Tuesday.

The counter-terrorism police were leading the probe "as a precaution because of associations that the man is believed to have had," the Metropolitan Police said. Police responded Monday night after reports that his body was found in the Kingston area of London, authorities said.

British media reported that the man was believed to be Nikolai Glushkov, a 69-year-old Russian exile who was close to a prominent critic of Russian President Vladimir Putin.

The Metropolitan Police said there was no evidence that suggested a link to last week's poisoning of former Russian spy Sergei Skripal and his daughter Yulia in Salisbury, England. The U.K. has said it was "highly likely" Russia was behind the poisoning, which left the pair in critical condition.

Glushkov was friends with Boris Berezovsky, a Russian oligarch who had criticized Putin and was found dead at his U.K. home in 2013, according to Sky News. A British inquest into Berezovsky's death concluded there was not enough evidence to determine how Berezovsky died, Sky News reported at the time.

Police in London said they believed they knew the identity of the deceased man but that the body had not yet been formally identified.

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Palestinian prime minister survives bomb blast

iStock/Thinkstock(NEW YORK) -- An apparent roadside bomb struck the convoy of Palestinian Prime Minister Rami Hamdallah Tuesday morning in the Gaza Strip, injuring several people, according to authorities.

Fatah, Hamdallah's political party that controls the West Bank, immediately called it an attempted assassination and said it holds Gaza's militant ruling party, Hamas, responsible.

The explosion went off shortly after his convoy entered the strip through the Erez Crossing with Israel, and the moment was caught on camera. In the video below, the blast hits at the 42 second mark.

Hamdallah was not hurt but according to video and photos from the scene, three of the vehicles were damaged, and one had blood on the door. The Palestinian Authority intelligence chief, Majid Faraj, was also traveling with Hamdallah.

 In a statement, Nabil Abu Rudeineh, spokesman of Palestinian President Mahmoud Abbas, who is based in the West Bank, said, “Hamas bears full responsibility for the cowardly targeting of the prime minister’s motorcade in Gaza.”

"Hamas opening an investigation is not enough," he said. "We need to find the full truth, and who is behind this attack."

“The attack against the government of consensus is an attack against the unity of the Palestinian people,” Rudeineh added.

 Hamas said the targeting of Hamdallah’s motorcade was “part of attempts to damage the security of Gaza and deal a blow to efforts to finalize reconciliation."

Hamdallah was in Gaza to cut the ribbon at a $75 million sewage plant project funded by The World Bank, European Union and other European governments that had been in the works for years. Immediately after the attack, he said he would go ahead with the visit and it would “not deter from seeking to end the bitter split. We will still come to Gaza.”

 Fatah and Hamas have been in a stand-off since Hamas won control over Gaza in 2007. Since then, Hamas has ruled the Gaza Strip while the Fatah Party have governed the West Bank, which is occupied by Israel. Hamdallah is now spearheading new negotiations to unify the two Palestinian factions.

Hamdallah returned safely to Ramallah in the West Bank and addressed the attack to an applauding crowd. “It was a well planned attempt," he said. "They planted explosive devices two meters deep."

Jason Greenblatt, President Trump's special representative for international negotiations who has been leading the effort in Israel and the Israeli-occupied Palestinian territories, was quick to condemn the attack on Twitter.

Meanwhile, Jared Kushner, President Trump's senior adviser and son-in-law, planned to hold a "brainstorming session" on the humanitarian crisis in Gaza. In a statement, the White House said Kushner "will present present specific proposals for consideration to help the people of Gaza." The Palestinian Authority said it would boycott the event.

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Russia 'not to blame' for former spy's poisoning, foreign minister says

ABC News(MOSCOW) -- Moscow "is not to blame" for the poisoning of a former Russian double agent in southern England last week, Foreign Minister Sergey Lavrov said today, though offering assistance in the investigation only if British authorities provide a sample of the nerve agent used in the attack.

Lavrov’s denial came in response to British Prime Minister Theresa May’s Monday comments that Russia was "highly likely" responsible for the chemical attack that left former spy Sergey Skripal and his daughter Yulia in critical condition while exposing at least 20 other people to the nerve agent in the sleepy English town of Salisbury.

May has given Russia until midnight Wednesday to provide a "credible" explanation for how what she called a Russian military-grade nerve agent came to be used in Skripal's poisoning, or face retaliation from Britain.

Lavrov, at a news conference today, said Russia is ready to assist in investigating the attack, but added that London would be "better off" complying with its international obligations "before putting forward ultimatums."

There has been little sign Russia is preparing to acquiesce to the British demands for an explanation. The Russian response so far been mostly bombastic denials and claims of a setup.

Russia’s foreign ministry today also mocked May's accusations and suggested they were an invention to smear Moscow.

“What PR man could come up with such a thing? Only someone at the level of Theresa May!” Maria Zakharova, a foreign ministry spokeswoman, wrote on her Facebook page.

The ministry’s official Twitter account posted a sarcastic message making “sincere thanks to Mrs. May for #HighlyLikelyRussia” accompanied by a video blaming Russia for the severe snowstorms that have caused gridlock the U.K. in the past month.

May told Parliament that investigators have identified the nerve agent used in the attack as of a variety known as a “Novichok,” a new generation of secret nerve poisons the Russia state is known to have developed. Britain has now demanded that Russia disclose the Novichok program to inspectors from the Organization for the Prohibition of Chemical Weapons (OPCW).

But a Russian senator today denied that Russia had any nerve agent stocks, saying they had been destroyed along with Russia’s entire chemical weapons arsenal. Igor Morozov, the senator, told state-operated RIA Novosti, “Russia not only halted the output of nerve-paralyzing gases, including ‘Novichok,’ but completely destroyed all its stocks of them.”

Russian President Vladimir Putin said in September that the country had completed the total dismantlement of its chemical weapons stocks. Russia has never acknowledged the existence of its Novichok program, even after Russian whistleblowers revealed it in the 1990s.
lerson Monday echoed the British assessment that although he didn’t know yet whether the Russian government knew in advance of the attack, there was no question the nerve agent "came from Russia."

“It is only in the hands of a very, very limited number of parties,” Tillerson told reporters, warning that the poisoning would “certainly trigger a response.”

Russia’s embassy in the United States attacked Tillerson’s comments as “fake news” in a statement to Russian news agency Interfax, accusing the U.K. and the Unite States of failing to provide any evidence.

Russian officials and commentators in state media have repeated an argument that killing Skripal’s would be of no benefit to Russia, noting that he had been pardoned when he was exchanged in a swap for Russian spies in 2010.

An officer in Russia's military intelligence service, Skripal sold information to Britain's MI6 spying agency in the late 1990s before he was arrested and convicted of high treason. Russian officials have said the new claims are part of an anti-Russian campaign that included the investigation into Russian election meddling in the United States.

“The same algorithm is being applied as in ‘Russia Gate’ in the U.S.,” Konstantin Kosachev, the head of Russia’s foreign affairs committee, whose comments often herald the Kremlin line, wrote in a Facebook post.

“A total presumption of guilt,” he wrote, where the accused is “not granted access to either the evidence or the process.” The West was turning to a “Stalinist” form of justice, he wrote.

Russian state television has suggested the poisoning, which led authorities to tell hundreds to wash their clothes as a precaution, could have been staged by British intelligence. Last week, an anchor on a main evening news broadcast also appeared to issue a warning to traitors.

Russia 24, a state news channel, invited a man alleged to have taken part in the previous major poisoning in the U.K. to participate in a panel show. Alexander Lugovoi, who, in a decade-long British inquiry, was alleged to have had killed dissident FSB officer Alexander Litvinenko with radioactive poison in 2006, told Interfax that May’s statements were “irresponsible.”

Lugovoi, who was made an MP in Russia's parliament after he was accused of the killing, said Britain was following the same "template" in the Skripal case. Russian authorities blocked British requests to help investigate Litvinenko's killing and to question Lugovoi, and the British inquiry concluded Putin had "probably" personally ordered the killing.

May said in her statement Monday that it Russia does not respond to the allegations by midnight Wednesday, Britain will treat the chemical attack as an “unlawful use of force” warranting retaliation. That could involve diplomatic expulsions, fresh sanctions and visa restrictions on wealthy Russians deemed close to the Kremlin, as well as potentially calling for increased NATO troop numbers in Eastern Europe.

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Clues about Meghan Markle's possible wedding dress designer

@kensingtonroyal/Instagram(LONDON) -- Designer Roland Mouret now appears to be the favorite to design Meghan Markle's wedding gown for her May nuptials with Prince Harry.

Mouret, a native of France who now calls London home, has remained tight-lipped about whether he has received the commission as Markle's designer.

His recent no comment reply to queries from Women’s Wear Daily about Markle have led many to speculate that Mouret is now the front-runner for the job.

"Mmmmm, I don’t want to say," Mouret told the fashion publication. "There is no comment on that. She’s a friend. And that's ... I can't say."

Mouret is a close friend of Markle, who was living in Los Angeles and Toronto before her engagement to Harry, 33, last November. The friends reportedly met Istanbul years ago.

Markle, 36, once shared that when she first met Mouret he said, "I [would] love to dress you."

"I thought 'What?' Then he told me who he was and we’ve been friends ever since," she recalled.

Mouret's fashion house is based in upscale Mayfair, in an affluent part of London. The designer debuted his first collection at London Fashion week in 1998 and has won numerous British fashion awards.

"Meghan knows really well what she likes and the main thing with Meghan is to listen to her and work in collaboration with her," he recently told the New York Post about Markle, adding, "I’ve already said too much."

Another top contender for designing Markle's gown is the design duo behind Ralph & Russo.

Australian-born designers Tamara Ralph and Michael Russo have already designed for Markle, creating the $75,000 dress she wore in her intimate engagement photos with Harry.

It is typical for designers of royal wedding gowns to remain quiet about their involvement. Sarah Burton, who designed the wedding dress of Princess Kate, denied being the dress designer before Kate and Prince William wed in 2011.

Markle mentioned several designers, including Narciso Rodriguez and Elie Saab, when she spoke to Glamour in 2016 about her dream wedding dress.

She told Glamour that the Narciso Rodriguez–designed white dress that Carolyn Bessette wore to her 1996 wedding to John F. Kennedy, Jr. is her favorite celebrity wedding dress, calling it "everything goals."

Royal watchers expect that Markle will select a designer who either has ties to Britain, her adopted home of Canada or the United States.

There has also been speculation that Markle could choose between two of Princess Diana's favorite designers, Catherine Walker and Amanda Wakeley, who both have couture shops near Kensington Palace.

Both Markle and Harry have said how important it is that Harry's late mother be included in their May 19th wedding, so it would be a sentimental surprise if Markle chose Walker or Wakeley.

Markle is expected to wear two gowns on her wedding day, one for the ceremony at St. George's Chapel at Windsor Castle and a more casual gown for the private evening reception that Harry's father, Prince Charles, is expected to throw for close friends and family.

Her stylist and friend from Toronto, Jessica Mulroney, has been by Markle's side helping guide her through the process. Mulroney flew to London in January to attend Markle's first fitting with her wedding dress designer.

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Novichok agents: All about the chemical weapon used in ex-Russian spy's poisoning

Michele Tantussi/Getty Images(NEW YORK) -- Speaking today, the United Kingdom's Prime Minister Theresa May identified the poison used in an attack on a former Russian spy and his daughter as a type of “military grade” nerve agent developed by Russia known as "Novichok."

Novichok — which means "newcomer" in Russian — is the codename for a series of nerve agents that Russia allegedly secretly developed in the latter stages of the Cold War. Novichok nerve agents were intended to be more powerful and harder to detect than previous generations of nerve agents.

Russia has never officially acknowledged the existence of the Novichok program and most of what is publicly known about it comes from Vil Mirzayanov, a Russian scientist who worked for years in the Soviet chemical weapons program.

Mirzayanov had been tasked with ensuring the secrecy of Russia’s chemical weapons program but came to believe the country was violating the Chemical Weapons Convention that it had recently signed onto with the United States. So in 1992, he and another scientist, Lev Fedorov, went public, writing an article first in the newspaper Moscow News and then giving interviews to Western journalists about the program.

According to the scientists, the Soviets had successfully developed a new type of so-called binary nerve agent. More common nerve agents such as sarin, VX and soman are usually unitary agents, meaning the component chemicals are mixed during manufacture and so the nerve agent is immediately dangerous; a binary agent, meanwhile, consists of two substances that must be combined in order to trigger their lethal effects.

In an academic article published in 1995 by the Stimson Center, Mirzayanov said he believed the first Novichok — known as Novichok No. 5 — was five to eight times more effective than VX gas, the lethal nerve agent that was used to assassinate the North Korean dictator Kim Jong Un’s half-brother, Kim Jong-Nam, last year.

Vladimir Uglev, another Soviet scientist, in 1998 told The Washington Post that one of the advantages of a Novichok precursor nerve agent, called A232, was that it could be frozen. Mirzayanov wrote the Novichok agents could also be created using more basic agricultural fertilizer materials, which he said was intended to make it easier to conceal their purpose from weapons inspectors.

Chemical weapons experts said the Novichok poisons work like other nerve agents: They attack a victim’s nervous system, causing them to lose control of bodily functions, prompting cardiac arrest and shutting down the respiratory system.

Novichok agents, however, are unusual for their strength, Gwynn Winfield, a chemical weapons expert with the publication CBRNe World, told ABC News. He said they required much larger doses of more complicated antidotes.

“Once you start talking about Novichok, you need far, far more,” Winfield said.

Winfield said that the Russian double agent Sergei Skripal and his daughter Yulia appeared to have been exposed to the nerve agent via their skin, since they left a trail around Salisbury, England, where they were found. Skripal could have picked it up from a contaminated object, but “equally there could have been an individual that just stood behind him while he was walking and just sprayed the back of his clothes and as it absorbed through the clothes it got on his skin,” Winfield said.

Winfield said he believes that the fact that Skripal and his daughter Yulia are still alive -- through in critical condition -- shows the assassins “messed up.”

“He should've been dead in five to 10 minutes,” he said. Other experts have said the window in which it took the Skripals to collapse was consistent with the effects of nerve agents.

May in her statement said the use of a Novichok-type agent meant either the Russian state had ordered the attack or else it had lost control of one of its chemical weapons. She said Russia has until midnight Wednesday to provide a “credible” response explaining that or otherwise the U.K. will retaliate. That retaliation is likely to include diplomatic expulsions, fresh sanctions and possibly increased troop deployments in eastern Europe.

Russia’s response so far has given no indication it will acquiesce. Maria Zakharova, a spokeswoman for Russia’s foreign ministry, called May’s allegations a “fairy tale” in comments to the news agency Interfax.

Britain’s foreign minister Boris Johnson has demanded that Russia provide “full and complete disclosure” of the Novichok program to the Organisation for the Prohibition of Chemical Weapons (OPCW).

While Russian authorities never acknowledged the Novichok agents, they inadvertently confirmed their existence when they charged Miryazanov with leaking state secrets in 1993. Under international pressure, the KGB dropped the case against Miryazanov, who eventually moved to the United States.

Mirzayanov wrote in the 1990s he believed Russia had created only "experimental quantities" of the Novichok agents, but that would still mean tens of tons. The Washington Post in 1998 quoted him that much of them had been blown up by Russia’s military to conceal their existence but he was unsure they had been entirely destroyed.

Cindy Vestergaard, a chemical weapons expert at the Stimson Center, said that nerve agents have recognizable signatures that can be matched to those usually used by different countries.

Winfield said he believed the use of Novichok agents on the Skripals was meant to send a message about Russia’s chemical weapons capabilities under President Vladimir Putin, who recently boasted of an array of elaborate additions to the country's nuclear arsenal as well.

“I think that's one of the reasons why it was chosen,” Winfield said. “It's a very clear signal not only to but also to the British government that there are exotic weapons out there that are far more terrifying than the ones we currently consider today.”

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More than 600 reptiles found as animal trafficking group dismantled: Europol

Europol(NEW YORK) --  Authorities broke up a Spanish criminal group trafficking rare animals after more than 600 reptiles were found, the European Union law enforcement agency Europol said today.

Nine people were arrested and seven others were under investigation, according to Europol, which said it aided in the operation to dismantle the group.

The reptiles were from North and South America, Asia, Africa, and Oceania, Europol said. The group brought the animals to Spain from Mexico, South Africa, Oman, Australia, New Zealand and the Fiji Islands, the agency said.

Authorities in 17 countries, including Spain's Civil Guard, were involved, according to Europol.

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British prime minister: 'Highly likely' Russia behind spy poisoning

Dan Kitwood/Getty Images(LONDON) -- British Prime Minister Theresa May told members of the Parliament today that it was "highly likely" Russia was responsible for poisoning Russian ex-spy Sergei Skripal and his daughter in England earlier this month.

She said Skripal, 66, and his daughter Yulia, 33, were exposed to a "military-grade nerve agent of a type developed by Russia." They were found slumped over in Salisbury, England, last week, and remained in critical condition.

May told members of Parliament that British authorities had concluded the Skripals were exposed to an agent that was part of the "Novichok" group of nerve agents developed by Russia.

Because Russia had produced the agent in the past and "would still be capable of doing so," it had sponsored assassinations before, and it saw some defectors as legitimate targets, the British government had "concluded that it is highly likely that Russia was responsible for the act against Sergei and Yulia Skripal," May said.

"Either this was a direct act by the Russian state against our country," May added, "or the Russian government lost control of its potentially catastrophically damaging nerve agent and allowed it to get into the hands of others."

The British foreign secretary has summoned the Russian ambassador to the United Kingdom to the British foreign ministry "and asked him to explain which of these two possibilities it is," May said. The foreign secretary, Boris Johnson, has requested a response by the end of Tuesday.

"Should there be no credible response, we will conclude that this action amounts to an unlawful use of force by the Russian State against the United Kingdom," May said.

May laid out a history of what she called "Russian state aggression" -- from annexing the territory of Crimea from Ukraine to a recent speech by Russian President Vladimir Putin where he unveiled weapons systems.

"This attempted murder using a weapons-grade nerve agent in a British town was not just a crime against the Skripals," May said. "It was an indiscriminate and reckless act against the United Kingdom, putting the lives of innocent civilians at risk. And we will not tolerate such a brazen attempt to murder innocent civilians on our soil."

A spokesman for Russia’s foreign ministry, Maria Zakharova, called May’s accusation a “circus show in the British Parliament,” according to Russian news agency Interfax.

“The conclusion is obvious: another information and political campaign based on provocation,” Zakharova told reporters, Interfax reported.

Skripal was a retired Russian double agent living in the U.K., convicted in Russia in 2006 for spying for Great Britain and released in 2010 as part of a prisoner swap.

This is a developing story. Please check back for updates.

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