Kurdish forces raise large banner of jailed PKK leader Abdullah Ocalan in iconic Raqqa square

US-backed Kurdish forces, who recently captured Raqqa from the Islamic State group, have raised a large image of jailed Kurdish leader Abdullah Ocalan in an iconic square of the Syrian city.

The Syrian Democratic Forces raised the banner in al-Naim square on Thursday, as allied female fighters gathered to hold a press conference, celebrating their contribution to the city's capture.

Ocalan is the leader of Turkey's outlawed Kurdistan Workers Party (PKK) who is jailed by Ankara.

He waged a decades-long insurgency in Turkey, where the PKK is considered a "terrorist" group.

He is idolised by many in the SDF and the closely allied YPG, which Ankara says is the Syrian branch of the PKK.

"The SDF have recently started hanging pictures of Ocalan in place of Syrian President Bashar al-Assad in schools and squares in Kurdish controlled areas," The New Arab correspondent Jalal Bakkour said.

"Observers believe the displays are evidence of the separatist aspirations of the Kurdish militias and a sign of defiance against Turkey and Syrian opposition groups, which classify the YGP as a terrorist group," Bakkour added.

SDF flags now cover al-Naim, where IS once displayed the severed heads of their enemies.

The SDF battled for more than four months, with US-led coalition support, to capture the city that was once the de facto Syrian capital of IS' self-styled "caliphate".

They announced the end of combat on Tuesday, though operations to clear explosives and seek out sleeper cells were ongoing.