Dozens of people had to be treated for breathing problems in the Syrian battlefront city of Aleppo after regime helicopters dropped barrel bombs on a rebel-held district Tuesday, a monitor said.
In addition, rebel gunfire killed five people in Azamiyeh, a government-controlled area in Aleppo, the Syrian Observatory for Human Rights said.
The bombs that left more than 70 people choking and in need of treatment were dropped from helicopters on the Sukkari neighbourhood, the Britain-based monitor said, adding most were civilians.
The opposition Aleppo Media Centre charged on its Twitter account that Sukkari was the target of a chlorine attack.
Observatory head Rami Abdel Rahman was unable to confirm the claim but said that no one was killed in the strikes.
A Sukkari resident told AFP a "very strong smell" filled the neighbourhood after it was hit by a barrel bomb and that he and others had difficulty breathing.
Both sides in Syria's complex war have traded accusations of attacks against civilians and use of unconventional weapons including chlorine and mustard gas.
Last month, an investigative panel set up by the UN Security Council said in a report that President Bashar al-Assad's forces had carried out at least two chemical attacks, one in 2014 and another in 2015.
But Syria's ally Russia said it had "very serious questions" about the report while the Syrian envoy to the world body, Bashar Jaafari, rejected the findings.
Meanwhile in the northwestern province of Idlib, most of which is under rebel control, eight people including two children were killed in regime air strikes, the Observatory said.