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

The Syrian Observatory for Human Rights said three separate suicide car bombings struck different locations in Tal Tamr, which is controlled by Kurdish forces and has been the target of attacks by the Islamic State jihadist group in the past.

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.

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

The Islamic State group overran much of the Khabur region in which Tal Tamr lies in February, and kidnapped at least 220 Assyrian Christians from the area during its 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 IS, according to the Assyrian Human Rights Network.