Six people, including three young children, were killed in an alleged regime gas attack late Monday in northwestern Syria, a monitoring group and activists said.
"Three children, their mother and father, and their grandmother suffocated to death after regime barrel bomb attacks" on their village in the province of Idlib, the Syrian Observatory for Human Rights said.
The Britain-based monitoring group said doctors in the village of Sarmin, southeast of the provincial capital of Idlib, concluded that the manner of death indicated a gas, possibly chlorine, had been emitted from the barrel bombs.
Sarmin's local coordinating committee, an activist group, said chlorine gas had been used and published photos of a chaotic field hospital where disoriented victims coughed and held gas masks over their faces.
It also posted videos of the pale bodies of the three children apparently killed in the attack. They appeared to have been no older than five and had dark circles around their eyes.
The Syrian regime has been accused of using chlorine -- a toxic agent that can be considered a chemical weapon -- on civilian areas in the past.
It has also been criticised by rights groups for using barrel bombs, crudely constructed weapons packed with explosives and typically dropped by helicopter.
Ibrahim al-Idlibi, an activist from the area, confirmed that six civilians had died of suffocation after two rounds of barrel bombs were dropped on the village.
"In the second round, civil defence volunteers were trying to protect the civilians by splashing water on them. But this is when they started suffocating," he said.
He told AFP that local doctors had not yet specified what the gas was.
In early March, the UN Security Council adopted a US-drafted resolution condemning the use of chlorine in Syria and threatening measures if chemicals are used in future attacks.