Raqqa Old City seized from Islamic State, US-backed Syria force says

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

"Our forces today seized full control of the Old City in Raqqa after clashes with Daesh," Syrian Democratic Forces (SDF) 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."

Most of IS's fighters and as many as 25,000 civilians may still be holed up in the city centre. 

The SDF's Arab and Kurdish fighters first broke into Raqqa in early June, penetrating its Old City a month later.

They were able to enter it after US-led coalition air strikes opened two gaps in the Rafiqah wall, a 2,500m barrier surrounding the Old City. 

The SDF has captured more than 60 percent of Raqqa city and most of the surrounding northern province.

Sello declined to say when the alliance expects to take the rest of Raqqa, but said operations were proceeding "according to schedule".

"Control over the Old City - which has historical importance - is a moral victory against IS, which is collapsing in Raqqa. Its defeat there is inevitable," he added.

The Syrian Observatory for Human Rights, a Britain-based monitoring group, said the SDF was still locked in clashes with IS in a small part of the Old City.

IS overran Raqqa in 2014, turning it into the de facto capital of its self-declared "caliphate".

The city was the scene of some of the group's worst atrocities, including public beheadings.