The Kurds "took control of the Al-Yaarubia border crossing with Iraq at dawn after clashes with the Islamic State in Iraq and the Levant, the Al-Nusra Front and other rebels," said the Syrian Observatory for Human Rights.

Al-Yaarubia is a strategic border town for both Kurds and jihadists as its serves as a major conduit for the flow of weapons and fighters from Iraq into Syria.

The clashes left fighters dead on both sides, said the Observatory, a Britain-based organisation that relies on a network of sources on the ground for its reports.

Observatory chief Rami Abdel Rahman told AFP that the Kurdish fighters "entered Al-Yaarubia town on Friday morning and seized control of part of it" after three days of fierce battles.

The Kurds made their move on Al-Yaarubia on Thursday after capturing four villages in the area and overrunning jihadist checkpoints, Abdel Rahman said.

Fighting was still ongoing Saturday, he added.

The Kurds and the jihadists have been fighting for months for control of northeastern Syria, an area rich in oil and wheat.

Arab tribes in the area have helped the Kurds advance but did not take part in the fighting this week which has left a large number of dead on both sides, the Observatory said giving without further details.

Rebels 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.