Raqa (Syria) (AFP) - Fighters from a US-backed coalition battling the Islamic State group in Syria walk among heavily damaged buildings in Raqa's Old City as snipers on upper floors monitor nearby jihadist positions.

The smell of decay rises from bodies of IS fighters killed in the battle for the key district as Syrian Democratic Forces field commander Ardlan Hasake patrols in an armoured Humvee.

"We pushed Daesh out of the whole of Raqa's Old City. It was their strategic centre and their main base for foreign fighters," he says, using an Arabic acronym for IS.

"All their forces were here and they tried repeatedly to attack us in large numbers to retake it, but our comrades repelled their attacks."

The SDF announced on Friday that it had taken full control of Raqa's Old City after fierce clashes with the jihadists seeking to defend what remains of their one-time Syrian bastion.

The Kurdish-Arab alliance, backed by an international coalition fighting IS in Syria and neighbouring Iraq, has seized more than half of the city since they first entered it in June.

In a nearby building, commanders lounge on the floor. One holds a tablet computer which he uses to map the positions of IS fighters in a street just south of the Old City wall.

An SDF unit then moves to the front line to strike the jihadists.

Snipers have installed firing points in the upper floors of buildings overlooking other parts of the city.

One of them sets up a rifle he nicknames "Zagros", after a mountain range that is home to many of the world's Kurds.

He trains his sights on an IS fighter near a mobile phone tower on the edge of the Old City, and prepares to squeeze the trigger.

- 'We pushed them back' -

A coalition air strike slams into a nearby street, sending clouds of grey smoke and dust billowing into the air.

"We're combing the streets around the Old City," Kurdish SDF commander Arkish Siyamand tells AFP.

"Daesh attacked some of our positions today (Sunday) but we pushed them back and the coalition bombed them."

Story continues

Seizing the Old City has put the SDF in a position dominating the city centre, which includes key IS security bases and some of Raqa's most densely packed neighbourhoods.

Siyamand says the jihadists are likely to try to retake the strategically vital Old City.

The SDF entered the Old City after coalition air strikes punched two holes in its Abbasid-era walls.

Parts of the wall have also been damaged, apparently by clashes.

Cars riddled with bullet holes sit at the entrances to side streets, evidence of intense combat.

In other parts of the Old City, SDF fighters have hung pink and brown curtains across major streets to allow them to move freely by blocking IS snipers' lines of sight.

The SDF's next target is a series of large grain silos around a kilometre (half a mile) south of the Old City.

Female snipers from the Kurdish Women's Protection Units sit on an upper floor of a building, monitoring IS fighters moving around the silos.

Biritan Judi, in her 20s, hovers a finger over the trigger of her rifle which protrudes from a window, the barrel resting on a decorated pillow.

"We monitor Daesh fighters and shoot them if they try to advance," she says.

"We're deployed in this strategic position and waiting for our prey from Daesh so we can smash their heads."