At least 50 civilians are being treated after a suspected poison gas attack by Syrian rebel groups on the government-held Aleppo city in the country’s north, according to reports in Syrian state media.

Most of those admitted to hospitals had breathing problems and blurred vision, doctors told state TV. One doctor said on Saturday two were in critical condition, including a child. State TV showed footage of medical professionals treating men and women on hospital beds.

There was a stench of gas in Aleppo city after projectiles were fired, said Rami Abdurrahman, the head of Britain-based Syrian Observatory for Human Rights.

Rebel commanders and opposition figures discredited the government reports, denying they lobbed gas into Aleppo and accusing Damascus of seeking to undermine an existing cease-fire and efforts to kickstart political talks. Earlier on Saturday, government shelling of a rebel-held area in neighbouring Idlib province killed at least seven civilians.

In Aleppo city, local governor Hussein Diab visited the injured at the hospital. He told state TV that 41 people had been admitted and accused rebels of using poisonous gas in the missiles they lobbed at the Aleppo neighbourhood.

Health official Haj Taha later said the number of injured was up to 50, adding that symptoms suggest the gas used was chlorine. Further tests are needed, he said.

A cease-fire in Aleppo and Idlib has been fraying in recent days. Aleppo has come under rebel attack in recent weeks, with missiles falling inside the city. The government has responded with counter attacks on rebel-held areas in the Aleppo countryside.

-AAP