Barrels suspected to contain chlorine gas have been dropped on Saraqeb town in Syria, reported a rebel faction as men, women and children had to be treated through out the night for breathing problems.
The attack took place in Saraqeb in Idlib province, near where a Russian military transport helicopter was shot down by rebels hours earlier.
About 30 people, mostly women and children, have been affected. Chlorine gas can cause victims to become short of breath and to foam blood from the mouth.
The government and some rebel groups have been accused of, and denied, using chemical agents.