By Nathan Morley
A response from Moscow was swift.
Russian Foreign Minister Sergei Lavrov said specialists had already visited the area of the alleged attack and did not find any trace of chlorine or any other chemical substance used against civilians.
In short, he said there was no evidence that an alleged chemical attack took place late Saturday, despite medical sources claiming dozens were killed by barrel bombs containing a lethal substance.
The attack in Douma was reported soon after Assad forces renewed their push on the last rebel enclave in eastern Ghouta.
Syria has repeatedly denied using chemical weapons.
Washington and Paris have both threatened a "joint, strong response.”
Meanwhile, Syrian and Russian authorities have claimed two Israeli jets flying over Lebanese air space opened an aerial attack on an air base in the Homes district on Monday.
There has been no comment from the Israeli military, but the Syrian Observatory for Human Rights – an independent monitoring group - said 14 people were killed, including troops from Iran.