Kurdish YPG forces are advancing this weekend against the ISIS-held town of Tel Abyad, the primary route from the ISIS capital of Raqqa to the Turkish border, and are threatening to cut off that key supply route for the Islamists.

YPG officials are confirming coordination with the US military on the attack, and several airstrikes carried out against ISIS forces in the town, the number of which is said to be growing as civilians flee the area toward the Turkish border.

ISIS still controls the town and the border road, but Kurdish officials say they believe it is "only a matter of time" before they take the area, a move which itself threatens to fuel more Turkish anger about the US government's close alliance with Kurdish forces in Syria.

Turkey has complained that the US is allied with Kurdish factions, like the YPG, which are considered "terrorist" organizations in Turkey, and fears Kurdish growth along the border threatens to ignite a new secessionist war among Kurds inside southeastern Turkey.