Syrian Kurdish fighters say they have taken control of the Islamic State-held town of Tal Abyad, cutting off a major supply route for the jihadist group.
Reinforcements are being sent by the Kurdish Popular Protection Units (YPG) to help secure the main road south to Islamic State's headquarters at Raqqa.
The fighting has prompted thousands of civilians to flee to nearby Turkey.
The YPG advance has been supported by Syrian rebel groups and air strikes by the US-led coalition against IS.
For the Kurds, capturing Tal Abyad allows them to link up the other pockets they control along the Turkish border, from Iraq in the east to Kobane in the west.
"The whole city is under our control and there is no more fighting," Huseyin Kocher, a Kurdish YPG commander in Tal Abyad told the BBC.
"Our people should know that we are going to clean all the remnants of IS in northern Syria."