Islamic State (IS) fighters have clashed with U.S.-backed forces in a militant stronghold in northern Syria.
The violence erupted after a 48-hour deadline given to IS militants to leave the encircled town of Manbij expired.
There are growing fears for the fate of tens of thousands of civilians trapped in Manbij, an IS stronghold that lies on a key supply route to the group's de facto capital of Raqqa.
U.S.-supported Kurdish-led Syrian Democratic Forces (SDF) have encircled Manbij but had avoided entering the town center in a bid to prevent civilian casualties.
The U.S.-led coalition air strikes have been blamed for the killing of at least 56 civilians in and around Manbij on July 19.