(Reuters) - At least 42 civilians including women and children have been killed in Syrian government air strikes on rebel-held territory in the country's northwest, a monitoring group said on Monday.

The attacks hit territory in and around the towns of Saraqeb and Ehsim in Idlib province on Sunday, the Britain-based Syrian Observatory for Human Rights said.

One struck an area outside Saraqeb where people who had fled earlier assaults on the town itself were taking shelter, the Observatory said.

It was not immediately clear what the attacks were targeting but an activist in the area said there were no rebel fighters near the positions they struck.

The Observatory, which monitors violence through a network of sources in Syria, said at least 16 children and 11 women were among the dead. At least 17 people from one family were also killed, it added.

One activist in Saraqeb said people had been fleeing to nearby farmland to escape the bombardment, but on Sunday warplanes also struck the farms which had been "packed with families".

"This is what led to the high number of deaths," the activist said.

The Observatory said the death toll from the strikes was expected to rise because many people were still in critical condition.