Syrian Kurdish-led forces said they had captured a town at the Turkish border from Islamic State on Monday, driving it away from the frontier in an advance backed by U.S.-led airstrikes that has thrust deep into the jihadis¡¯ Syria stronghold.

The capture of Tel Abyad by the Kurdish YPG and smaller Syrian rebel groups means the Syrian Kurds effectively control some 400 km (250 miles) of the Syrian-Turkish border that has been a conduit for foreign fighters joining Islamic State.

While the advance has brought the well-organized YPG deep into Islamic State¡¯s stronghold of Raqqa province, it has also concerned Turkey, which is worried the expansion of Kurdish sway risks inflaming separatist sentiment among its Kurdish minority.