Defence Ministry, Israel carried out the attack by launching eight guided missiles from two F-15 planes, and Syria shot down five of the missiles. "Get ready Russian Federation, because they will be coming, nice and new and 'smart!' You shouldn't be partners with a Gas Killing Animal who kills his people and enjoys it!"
The US and France warned of a strong response to "horrific chemical weapons attacks" on the rebel-held area near Damascus.
"Our military specialists have visited this place. and they did not find any trace of chlorine or any other chemical substance used against civilians", he said.
Iran is a key ally of the Syrian government, alongside Russian Federation, and Velayati was speaking on arrival in Damascus where he was due to meet with President Bashar al-Assad, according to ISNA.
Jonathan Schanzer, the senior vice president at the Foundation for Defense of Democracies, also predicted a looming "showdown" between Israel and Iran on Syrian soil, going so far as anticipating the Middle East's "worst war" in decades.
Human rights groups and United Nations officials say the tactic amounts to forced displacement, a war crime.
More than 500 people, mostly women and children, were brought to medical centres complaining of difficulties breathing, foaming at the mouth and burning sensations in the eyes.
The Observatory gave a higher death toll, saying at least 80 people were killed in Douma, including around 40 who died from suffocation.
The Syrian government denied the allegations, calling them "fabrications" by the Army of Islam and a "failed attempt" to impede government advances.
"With the Syrian army having the upper hand on the ground against the armed terrorists, it would not be rational for it to use chemical weapons", the statement said.
Russian Federation and Syria deny that chemical weapons were used.
In recent weeks, government forces have recaptured villages and towns in the eastern Ghouta suburbs of the capital.
"A president who says he wants to get the hell out of Syria is not really in a position to threaten the military progress of the regime", he said.
"Accepting Iranian entrenchment in Syria would be to accept Iranians putting a chokehold on us".