SDF fighters began advancing toward Raqqa in November, capturing wide areas from the extremists.

A U.S.-backed Syrian force has said it has begun an offensive to capture the northern city of Raqqa, the de facto capital of the Islamic State group.

Talal Sillo, a spokesman for the Kurdish-led Syrian Democratic Forces, told reporters on Tuesday that operations have begun in coordination with the U.S.-led coalition.

SDF fighters began advancing toward Raqqa in November, capturing wide areas from the extremists. Last week, they reached the northern and eastern gates of the city.

Raqqa is currently surrounded from the east, north and west, and opposition activists have reported intense shelling on the city since Monday night, which killed at least 12 people.