At least 22 people were killed by three truck bombs in a Kurdish-controlled town in northeastern Syria, the Syrian Observatory for Human Rights reported on Friday.
It said the death toll from the attack in Tel Tamer late on Thursday was likely to increase.
The town in the northeastern province of Hasaska is controlled by the Kurdish YPG militia, which has been battling Islamic State with the support of U.S.-led air strikes.
The Observatory said one of the bombs exploded near a health center, and another near a vegetable market. It said there was “confirmed information” about casualties among the Kurdish internal security force known as the Asayish. Asayish officials could not immediately be reached for comment.
The YPG has been the most effective partner on the ground in Syria for the US-led alliance. In October, it became part of a new US-backed alliance called the Democratic Forces of Syria.