A triple truck-bomb attack carried out by Islamic State in north-eastern Syria killed at least 50 people and wounded 80 others, a spokesman for the Kurdish militia that controls the area has said.

The town, in the province of Hasaka, is controlled by the Kurdish YPG militia, which has been battling Isis with the support of US-led airstrikes. Kurdish fighters have advanced in the province in recent weeks, notably with the takeover of the town of al-Houl by a US-backed rebel alliance that includes the YPG.

The three blasts, carried out by at least two suicide bombers, hit outside a hospital, at a market and in a residential area in the town of Tel Tamer late on Thursday, the YPG’s Redur Xelil said. “There is massive destruction in the town, and the number killed is between 50 and 60, all of them civilians,” he added.

The UK-based Syrian Observatory for Human Rights gave an earlier death toll of at least 22 but said the number was likely to increase.

Amaq news agency, which supports Isis, said the militant group had carried out the attack, targeting Kurdish “bases” in Tel Tamer with three suicide bombs.

The observatory said there was confirmed information about casualties among the Kurdish internal security force, known as the Asayish.

The YPG has been the coalition’s most effective partner on the ground in Syria. In October, it became part of the new US-backed alliance, the Democratic Forces of Syria.