Islamic State fighters captured territory from Syrian rebels near the Turkish border on Friday and inched closer to a town on a supply route for foreign-backed insurgents fighting the jihadists, a monitoring group said.
The hardline group has been fighting against rebels in the area for several months. The rebels, who are supplied via Turkey, last month staged a major push against Islamic State, but the group counter-attacked and beat them back.
The United States has identified the area north of Syria's former commercial hub Aleppo as a priority in the fight against the Islamic State group (IS).
The British-based Syrian Observatory for Human Rights said Friday's advance was the biggest by IS in Aleppo province for two years. It brought the jihadists to within 5 km (3 miles) of Azaz, a town near the border with Turkey through which insurgents have been supplied.