The al Qaeda-linked Nusra Front says it has quit frontline positions against Islamic State north of Aleppo and ceded them to other rebels, leaving an area of northern Syria whereTurkey wants to set up a buffer zone.

A Nusra Front statement dated Sunday criticized a Turkish-U.S. plan to drive Islamic State from the Syrian-Turkish border area, saying the aim was to serve “Turkey’s national security” rather than the fight against President Bashar al-Assad.

The United States and Turkey last month announced their intention to drive Islamic State from a strip of territory in northern Syria near the Turkish border in a campaign that would provide air cover for Syrian rebels in the area. […]