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Russian Defense Ministry spokesman, Maj. Gen. Igor Konashenkov, said Britain was "directly involved” in the Douma episode but didn't elaborate or provide evidence.
Activists and aid groups say dozens died in the assault on Douma, the last rebel stronghold in eastern Ghouta, which has been subjected to intensive bombing by Syria's Russian-backed regime of President Bashar al-Assad.
The samples suggested the presence of both chlorine gas and an unnamed nerve agent, two officials said.
Assad is known to have stocks of the nerve agent sarin, and has previously used a mixture of chlorine and sarin in attacks, according to U.S. officials.
Russia also tangled with the United States at the U.N. Security Council on Friday.
U.S. Ambassador to the U.N., Nikki Haley, said Russia was the only country to have defended Syria’s use of chemical weapons, adding: “No one is buying its lives and its cover-ups.”
She said Assad’s government had used chemical weapons at least 50 times during the six-year conflict.
“The world must not passively accept the use of chemical weapons,” she told delegates. “Everything the U.N. stands for is being blatantly defied in Syria with the help of a permanent member of this council. All nations, all people will be harmed if we allow Assad to normalizer the use of chemical weapons.”