President Bashar al-Assad's forces have used chemical weapons more than two dozen times during Syria's civil war, including in a deadly attack in April, UN war crimes investigators say.
The latest report by the UN Commission of Inquiry on Syria on September 6 offers some of the most conclusive evidence yet of allegations that Assad's forces carried out the April 4 attack on Khan Sheikhun in which more than 80 civilians were killed.
"Government forces continued the pattern of using chemical weapons against civilians in opposition-held areas. In the gravest incident, the Syrian Air Force used sarin in Khan Sheikhun, Idlib, killing dozens, the majority of whom were women and children," the UN report said, declaring the attack a war crime.
A government warplane dropped sarin, an odorless nerve agent, on the town in rebel-held Idlib Province, the commission said.
The United States at the time immediately blamed Assad's government and launched a punitive strike on Shayrat air base, where the report says the plane took off.
In their 14th report since 2011, UN investigators said 33 chemical-weapons attacks had been documented so far.
Twenty-seven were by Assad's government. Perpetrators had not been identified yet in six attacks, they said.
The Assad government has repeatedly denied using chemical weapons. It said its strikes in Khan Sheikhun hit a weapons depot belonging to rebel forces, a claim "excluded" by commission Chairman Paulo Pinheiro at a news conference in Geneva.
The weapons used on Khan Sheikhun were previously identified as containing sarin, but that finding by a fact-finding mission of the Organization for the Prohibition of Chemical Weapons (OPCW) did not specify who was responsible.
The panel also said U.S. air strikes on a mosque in Al-Jina in rural Aleppo in March that killed 38 people, including children, failed to take precautions in violation of international law, but did not constitute a war crime.