At least 35 people, including nine children, were killed in an air strike that released "toxic gas", possibly chlorine, on the rebel-held town of Khan Sheikhun in Syria's central Idlib Province on Tuesday, according to the British-based Syrian Observatory for Human Rights.
The opposition group said that medical sources in the town reported symptoms among the affected including fainting, vomiting and foaming at the mouth. The monitoring group was unable to confirm the nature of the substance, and said it was unclear if the planes involved in the attack were Syrian or those of government ally Russia.