Fierce clashes erupted in Syria overnight between Kurdish fighters and jihadists near the Iraqi border, the Syrian Observatory for Human Rights said Thursday.
"The clashes began around midnight (2100 GMT Wednesday) and lasted around 12 hours, with the Kurds advancing in the direction of Al-Yaarubia, an area controlled by the Islamic State of Iraq and the Levant (ISIL) and other jihadist groups," the Britain-based monitor said.
"The Kurds have managed to take two villages controlled by the jihadists but it will be difficult to capture Al-Yaarubia from ISIL," Observatory director Rami Abdel Rahman told AFP.
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The Al-Yaarubia border crossing with Iraq is seen as a key supply route for arms and fighters. ISIL has carried out attacks on both sides of the border.
The Kurds and the jihadists have been fighting for control of northeastern Syria, an area rich in oil and wheat, for months.
Rebels ostensibly fighting to overthrow President Bashar al-Assad have increasingly turned their guns on each other in recent months, with jihadists clashing with the mainstream Free Syrian Army in the north, where the rebels control vast swathes of territory.
Kurdish fighters affiliated with Turkey's separatist Kurdistan Workers' Party (PKK) have meanwhile struggled to carve out an autonomous region in northeastern Syria similar to one in northern Iraq.