Russia on Friday said it had proof the Syrian government was not behind a new spate of alleged chemical attacks in the country, amid fresh international calls for a probe.
"Accusations against government forces continue to be fabricated about alleged cases of them using chemical substances," said a Russian foreign ministry statement.
"The Russian side has authentic information that such statements are false," it said.
United Nations Security Council members this week called for a new probe into claims of chlorine gas attacks in Syria, with the government and opposition both accusing the other of chemical attacks in rebel-held provinces.
France and the United States allege that Assad's forces may have unleashed industrial chemicals on a rebel-held village in central Hama province this month.
Activists have also reported chlorine gas attacks, most recently in the northwestern Idlib province on Monday.
"This, yet another anti-Syrian 'chemical' hysteria, highlights the question of the real goals of its initiators, who are not abandoning attempts to find a reason for intervention in Syria," said the statement.
Meanwhile, the joint task force from the UN and Organisation for the Prohibition of Chemical Weapons said this week that Syria has nearly completed the hand-over of its chemical weapons stockpile.
Damascus had pledged to have all stockpile removed from the war-ravaged country by Sunday. The weapons are then to be destroyed by June 30.