US-backed fighters on Friday ousted the Islamic State group from Raqa's Old City, a spokesman told AFP, bringing them closer than ever to the jihadists' most well-defended positions.

"Our forces today seized full control of the Old City in Raqa after clashes with Daesh," Syrian Democratic Forces spokesman Talal Sello said, using the Arabic acronym for IS.

"We are on the edges of IS's security quarter in the city centre, where most of its main bases are."