US-led strikes targeting the Islamic State group have killed at least 52 civilians in northern Syria, activists say, but the Pentagon says it can not confirm the report.

The opposition Britain-based Syrian Observatory for Human Rights also reported 10 civilian deaths in a rocket strike on Saturday in the northern city of Aleppo and said 40 others suffered respiratory problems in a pre-dawn chemical attack further north in Idlib province.

Observatory director Rami Abdel Rahman said that US-led coalition strikes early on Friday on the village of Birmahle in Aleppo province killed 52 civilians.

He said “seven children” were among the dead but that the toll could rise as 13 people were still trapped under rubble.

Kurdish militiamen and Syrian rebel fighters were clashing with IS jihadists in a town roughly two kilometres away from Birmahle at the time of the strikes.

“Not a single IS fighter” was killed in the strikes on Birmahle, said Abdel Rahman, adding that the village is inhabited by civilians only and that IS has no positions there.

US Central Command spokesman Colonel Patrick Ryder said there was “no information to corroborate allegations that coalition air strikes resulted in civilian casualties”.

“Regardless, we take all allegations seriously and will look into them further,” he added.

News of the deaths come as Canadian Prime Minister Stephen Harper visited Iraq, days after MPs in Ottawa voted to expand their country’s contribution to the US-led coalition against IS.

Air strikes by the international coalition have supported Kurdish militias fighting IS in Aleppo province, most notably in the flashpoint border town of Kobane, which is near Birmahle.

Backed by the strikes, Kurdish fighters drove jihadists out of Kobane in January.

A statement released on Friday by the coalition’s joint task force said it had conducted six air strikes near Kobane on IS tactical units.

In Aleppo, at least 10 civilians, including three children, were killed in rebel rocket attacks on Saturday on regime-controlled parts of the divided city.

Syrian state television blamed “terrorists” for the rocket attacks, which it said killed 12 people and wounded 45.

Also on Saturday, at least 40 civilians, including children, suffered respiratory problems in “chlorine gas attacks” on two rebel-held villages in northwestern Idlib province, activists said.

The Observatory said regime forces dropped barrel bombs filled with chlorine on Saraqeb and Nairab causing the deaths.

A video posted by activists online showed paramedics splashing a toddler with water, while other children – some coughing – breathed through gas masks.

The video could not be independently verified.