(MOSCOW) -- Russia is urging the Syrian government to allow U.N. inspectors to investigate claims of a chemical weapons attack outside Damascus this week.
In a statement issued Friday, the Russian Foreign Ministry also urged Syria's armed opposition to provide the inspectors safe passage to the site of the alleged attack.
Those inspectors are already in the country. They arrived Sunday to investigate earlier claims of another chemical weapons attack near Aleppo.
The Syrian government has denied any involvement in the incident but has not yet said whether it would allow the U.N. team to investigate.
With its statement Friday, Russia joined calls from the United States and its European allies for an independent investigation into the alleged attack, which rebel groups claim killed at least 1,000 people.
But Russia also cast doubt on claims by those groups that the Syrian government was responsible, suggesting that the evidence was prepared in advance in order to frame the government.
"We're getting more new evidence that this criminal act was of a provocative nature," a Russian Foreign Ministry spokesman said in a subsequent statement, suggesting the attack was "pre-planned."
"There are reports circulating on the Internet, in particular that the materials of the incident and accusations against government troops had been posted for several hours before the so-called attack. Thus, it was a pre-planned action," Alexander Lukashevich said.
Russia's doubts came as Britain's Foreign Secretary blamed government forces for the attack.
William Hague said Britain believes the attacks were carried out "by the Assad regime on a large scale."
"This is not something that a humane or civilized world can ignore," he said. Syrian opposition forces said the attack happened early Wednesday morning. Graphic videos posted online show rows of dead bodies, including several children, with no outward signs of trauma. Survivors are seen convulsing and doctors in the videos claim the injuries show the tell-tale signs of a chemical or nerve agent attack.
Russia was also skeptical of rebel claims that the government carried out its first chemical weapons attack near Aleppo in March. The Kremlin has been reluctant to abandon Syria's President Bashar al-Assad, a long-time ally and purchaser of Russian arms. Those arms have continued to flow during the two-and-a-half year conflict. Russia has repeatedly blocked attempts to impose sanctions, including an arms embargo, on the Assad government at the U.N. Security Council. Earlier this week, Russia and China reportedly worked behind the scenes to water down a Security Council statement on the latest alleged chemical weapons attack.
Last year, President Obama described a chemical weapons attack in Syria as a "red line" that would prompt greater action by the United States. After reports of the March attack surfaced, the Obama administration said it would step up material aid to certain rebel groups, but recent reports suggest the United States has yet to begin doing so on a large scale.
In an interview with CNN that aired Friday, President Obama said preliminary reports of this week's second chemical weapons attack indicate a "big event of grave concern."
"It is very troublesome. That starts getting to some core national interests that the United States has, both in terms of us making sure that weapons of mass destruction are not proliferating, as well as needing to protect our allies, our bases in the region," he said, without offering any indication of how the United States might respond.
On Thursday, Secretary of State John Kerry called his Russian counterpart Sergei Lavrov, according to a Russian Foreign Ministry statement. The two discussed Syria and agreed on the need for an "impartial" investigation into the latest alleged chemical weapons attack, the statement said.
American and Russian officials are set to meet next week to discuss plans for a long-delayed conference on Syria, which hopes to bring both the Assad government and the rebel groups to the table.
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