Air strikes killed at least 58 people, including 11 children, and wounded dozens in the northwestern Syrian province of Idlib on Tuesday, the Syrian Observatory for Human rights said.
The toxic gas attack took place in the town of Khan Sheikhoun, in the central province of Idlib, early Tuesday morning.
It is believed that another 60 of the approximately 200 people exposed to the gas were injured in the attack.
Reports citing the Idlib Health Directorate, however, say that up to 100 people could be dead from the gas attack, and another 400 are injured.
The Syrian Observatory for Human Rights said those killed had died from suffocation and the effects of the gas.
Photos and video emerging the incident show children to adults limp and suffering from breathing difficulties. Some appear foaming at the mouth.
The victims were mostly civilians, it said, and included at least nine children.
Syrian government or Russian jets pounded the town of Khan Sheikhoun in rebel-held Idlib in the morning, the Britain-based war monitoring group said.
The Syrian army could not immediately be reached for comment, but a Syrian military source said last week allegations that government forces were using chemical weapons were ‘devoid of truth’.
A Syrian military source denied that government forces used any such weapons, saying the army ‘does not and has not’ used chemical weapons ‘not in the past and not in the future’.