Syrian government air strikes killed at least 42 people, including 16 children, in Idlib province in the northwest, the Syrian Observatory for Human Rights said on Monday.
The air raids on Sunday afternoon and evening killed 19 people, including six children, outside the city of Saraqeb, and another 23 people, among them 10 children, in the town of Ehsim, the monitoring group said.
The province is largely under rebel control outside its capital, Idlib city.
The strikes outside Saraqeb hit an area where civilians were sheltering after fleeing repeated government air strikes on the city, the Observatory said.
Footage of the aftermath of the attack in Ehsim posted on YouTube by activists showed desperate civilians trying to dig out a man buried up to his neck in the rubble of a collapsed building.
Another video showed the lifeless body of a child, naked and covered in grey dust, lying on top of shattered breeze blocks.
Young men recovered the body and carried it away in a black shroud, shouting "God is greater."