The international chemical weapons watchdog says chlorine was likely used as a weapon in the Syrian town of Saraqeb in early February, the latest report of poison gas being unleashed in Syria's civil war.

The Organization for the Prohibition of Chemical Weapons released details of a report into the chlorine use on Wednesday. The OPCW is not mandated to apportion blame for the attack.

The OPCW says its Fact-Finding Mission probing alleged use of chemical weapons in Syria "determined that chlorine was released from cylinders by mechanical impact in the Al Talil neighbourhood of Saraqib."

The mission also is investigating allegations that poison gas was used in Douma, near the capital Damascus, in a deadly April 7 attack. It has not yet issued a report on that attack.