Syrian activists say civilians have suffered chlorine gas poisoning during an attack on the rebel-held town of Saraqeb in Idlib province.
The attack comes a day after Syria's former al-Qaeda affiliate claimed responsibility for the downing of a Russian warplane as it flew low over Saraqeb in northern Syria, apparently using a surface-to-air missile.
The pilot was killed after he ejected and exchanged gunfire with militants on the ground, the Russian Defence Ministry and a monitoring group said.
Hayat Tahrir al-Sham, or HTS, a powerful rebel alliance that publicly split from al-Qaeda last year, said it had used a man-portable antiaircraft system to shoot down the Su-25 fighter jet.
Saraqeb has come under heavy bombardment from Russian and Syrian warplanes in recent days as pro-government forces try to recapture a strategic highway linking Damascus to Aleppo.
