TEHRAN - Iran said Friday that it "strongly condemns" a US air strike on a Syrian government airbase in retaliation for a suspected chemical weapons attack on a rebel-held town.

"We condemn all unilateral military action and the missile strike by US warships against Shayrat airbase under the pretext of Tuesday's suspected attack on Khan Sheikhun," foreign ministry spokesman Bahram Ghassemi told the Fars news agency.

Iran, with Russia, is the closest ally of the regime of President Bashar al-Assad and has provided money, weapons, military advisers and trainers, as well as volunteer militiamen to support it in the six-year civil war.

Its spokesman said that the US strike would merely "help the terrorist groups, which are on the back foot, and further complicate the situation in Syria and in the region."

Both Tehran and Moscow have said that Tuesday's deaths of dozens of civilians in Khan Sheikhun in northwestern Syria were the result not of a regime chemical attack but of toxic substances that had been stockpiled by jihadists on the ground and released by a conventional strike.

On Wednesday, Iran condemned all use of chemical weapons and called for the destruction of stocks held by "armed terrorist groups" in Syria.-AFP