杭州龙凤Medical sources say dozens were killed in Saturday’s alleged attack but numbers are impossible to verify.
Mr Lavrov said Russian specialists and aid workers had visited the area, which rebel fighters have started leaving under a surrender deal.
The US and France have threatened a “joint, strong response”.
The claim from Russia – which has intervened militarily in Syria in support of the government – came after videos shot by rescue workers on Saturday showed lifeless bodies of men, women and children with foam at their mouths.
The estimates of how many people died range from 42 to more than 60 people, but medical groups say numbers could rise as rescue workers gain access to basements where hundreds of families had sought refuge.
The UN Security Council is to discuss the allegations later on Monday.杭州龙凤
Mr Lavrov spoke hours after a deadly attack on a Syrian military airbase, which Moscow and the Syrian government blamed on Israel.
Missiles hit the Tiyas facility, known as T4, near the city of Homs. Fourteen people are said to have been killed, including three Iranians.
Israel, which has previously hit Syrian targets, has not commented. Syria initially blamed Washington for the strike, but the US, UK and France have all denied involvement.
It is unclear whether the strike had anything to do with the suspected chemical attack.杭州龙凤