BEIRUT (AP) — A car bomb exploded at a checkpoint manned by Turkey-backed opposition fighters in northeast Syria killing at least four people Thursday, local officials and Syrian opposition activists said.

The governor's office of Turkey's southern Sanliurfa region said in a statement on its website that one gendarmerie corporal and three local security personnel were killed in the attack.

It blamed Kurdish militants for the blast on the road leading to the Syrian town of Ras al-Ayn Thursday afternoon.

The Britain-based Syrian Observatory for Human Rights, an opposition war monitor, said the blast killed five, including three Turkey-backed opposition fighters and two members of Turkey's paramilitary force.

The governor's office said 10 others were wounded, including seven civilians, who were being treated in the Turkish border village of Ceylanpinar and their conditions were stable.

Turkey has blamed explosions that killed and wounded dozens of people in northeast Syria in recent months on Kurdish fighters.

Ankara views the Kurdish fighters as terrorists for their links to a Kurdish insurgency inside Turkey. The Kurdish fighters had, however, partnered with the U.S. against the Islamic State group.