At least 12 people were killed and dozens wounded on Thursday in a triple suicide car bomb attack in northeastern Syria's Hasakeh province, a monitor said.

The Syrian Observatory for Human Rights, updating an earlier death toll of 10, said suicide car bombs struck three different locations in Tal Tamr, which is controlled by Kurdish forces and has been the target of past attacks by the Islamic State (ISIS) group.

The Britain-based monitor's chief, Rami Abdel Rahman, said it was not immediately clear if all the casualties were civilians, noting that one of the blasts took place in front of a local security post.

State television also reported the blasts, saying at least nine people had been killed and dozens injured.

In February, ISIS overran much of the Khabur region, in which Tal Tamr lies, and kidnapped at least 220 Assyrian Christians during the offensive.

But Kurdish fighters from the People's Protection Units (YPG) subsequently recaptured the region, and dozens of the IS-held hostages have been released in recent months.

On Wednesday, some 25 Assyrian hostages, including two children, were freed by ISIS, according to the Assyrian Human Rights Network.