Syrian regime helicopters dropped on Tuesday barrel bombs containing chlorine gas on al-Sukari neighbourhood in the rebel-held east side of Aleppo, activists said.
"Medical sources said 70 people suffered from suffocation and breathing problems after a regime helicopter raided the area,” said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights.
Ibrahim al-Hajj, spokesman for the White Helmets, a volunteer civil defence organization that operates throughout opposition-controlled Syria, confirmed to dpa that at least 80 people, including 50 women and children, were treated for breathing problems and that the smell of chlorine gas filled the area.
A video posted by the White Helmets on YouTube showed rescue workers sifting through the rubble for survivors in smoke-filled air. Paramedics had begun undressing and washing victims with water, including children.
“He smells like chlorine all over," one paramedic is heard saying while washing up a child.
The video also showed a crowded hospital where people of different ages seemed to have breathing difficulties; some appeared with oxygen masks while others were taking nebulizer sessions as they were being injected with medications.
Last month, the UN Security Council said perpetrators of chemical weapons attacks in Syria must face accountability, after a UN report confirmed that the Syrian government and Islamic State extremists have used such weapons in recent years.
In 2013 the Syrian government signed up to an international convention banning chemical weapons stockpiles, after it was widely blamed for a chemical weapons attack on rebel-held Damascus suburbs in which hundreds of civilians were killed.