At least 42 people, including children, were killed on Sunday when Syrian army helicopters dropped improvised "barrel bombs" in the northern province of Aleppo, a monitoring group said.

The British-based Syrian Observatory for Human Rights said separate air raids hit several districts in Aleppo, but the biggest toll was in Hanano, east of the city. At least six children were among the dead.

"They hit a convoy of cars on a road in Hanano, many cars were destroyed. There were civilians there," said the Observatory's Rami Abdelrahman.