UN vehicle transporting a team of chemical experts
UN vehicle transporting a team of chemical expertsReuters

The Organization for the Prohibition of Chemical Weapons (OPCW), the world's chemical weapons watchdog, said Wednesday it was "disturbed" by the alleged use of toxic chemicals in Aleppo after dozens of people had to be treated for breathing problems in the Syrian battlefront city.

"We are disturbed by the recent allegations of the use of toxic chemicals in Aleppo," said a statement by the director-general of the Hague-based OPCW, Ahmet Uzumcu, quoted by AFP.

"Such allegations are taken very seriously. The use of chemical weapons by anyone, anywhere and under any circumstances is unacceptable," he added.

The statement comes a day after more than 70 people were left choking after regime helicopters dropped barrel bombs on a rebel-held district of the war-ravaged city, the Syrian Observatory for Human Rights said.

The bombs left people in need of treatment, the British-based monitor said, adding most were civilians.

The opposition Aleppo Media Center said on its Twitter account that the Sukkari neighborhood was the target of a chlorine attack.

Observatory head Rami Abdel Rahman was unable to confirm the claim, but said no one was killed in the strikes.

The alleged chlorine attack on Aleppo came days after a UN-led investigation blamed the Syrian regime for at least two chemical attacks, one in 2014 and another in 2015.

Previous reports from the OPCW had concluded that toxic gases have been used as weapons in Syria's five-year war, but stopped short of identifying the perpetrators.

Both sides in Syria's complex civil war have traded accusations of attacks against civilians and use of unconventional weapons including chlorine and mustard gas.

The government in Damascus argues that claims that it used chemical weapons are only meant to "serve political agendas".

Syria's ally Russia said it had "very serious questions" about the latest report while the Syrian envoy to the world body, Bashar Jaafari, rejected the findings.

AFP contributed to this report.