The Syrian Observatory for Human Rights said more than 11 people were killed and 35 wounded by air strikes in the town of al-Sur in northern Deir al-Zor province on Tuesday, Reuters reported.
The death toll was expected to rise because of the number of serious injuries, the British-based monitoring group said.
It was not immediately clear which air force had carried out the strikes, but they took place in an area where the U.S.-led coalition fighting Islamic State has been operating, the Observatory said.
Deir al-Zor province is almost fully under Islamic State control.