SINJAR, Iraq -- Supported by U.S.-led airstrikes, Kurdish Iraqi troops seized part of a highway Thursday that is used as a vital supply line by the Islamic State group, a key initial step in a major offensive to retake the strategic town of Sinjar from the militants.

The town was overrun by the extremists as they rampaged across Iraq in August 2014, leading to the killing, enslavement and flight of thousands of people from the minority Yazidi community. The U.S. later launched an air campaign against the Islamic State militants, also known as ISIL, ISIS and, in Arabic, as Daesh.

Hours into Thursday's operation, the Kurdish Regional Security Council said its forces controlled a section of Highway 47, which passes by Sinjar and indirectly links the militants' two biggest strongholds -- Raqqa in Syria and Mosul in northern Iraq -- as a route for goods, weapons and fighters.

Coalition-backed Kurdish fighters on both sides of the border are trying to retake sections of that corridor as part of Operation Free Sinjar.

"By controlling Highway 47, which is used by Daesh to transport weapons, fighters, illicit oil and other commodities that fund their operations, the coalition intends to increase pressure ... and isolate their components from each other," a coalition statement said. It said more than 95 miles of territory had been retaken from ISIL.