UN human rights investigators say they have strong suspicions but not absolute proof that Syrian rebel forces have used the nerve gas sarin.
It follows interviews with victims and doctors in neighbouring countries.
“We collected some witness testimony that made to appear that some chemical weapons were used, in particular nerving (sic) gas and what appears to our investigation (was) that that was used by the opponents, by the rebels,” said Carla del Ponte, a member of the UN investigating team who has also served as an international war crimes prosecutor.
The Geneva-based inquiry gave no details as to when or where the nerve gas may have been used.
It did not find evidence that government forces had resorted to chemical weapons.
The US has said it has “varying degrees of confidence” that Syria’s government has used sarin on its people.
Both President al-Assad’s forces and the rebels have accused each other of employing chemical weapons several times.
Sarin has no colour or smell and can be fatal even in small doses.