RAQQA (Syria) • Joyous fighters from the US-backed Syrian Democratic Forces (SDF) yesterday raised their yellow flag in Raqqa's Al-Naim traffic circle, which became known as "Hell Roundabout" after it was used for gruesome public executions by the Islamic State in Iraq and Syria (ISIS).

"Hell Roundabout is now Al-Naim Roundabout again," declared the cheering fighters, surrounded by crushed buildings and charred cars damaged in the ferocious battle for the city.

They were celebrating after taking full control of the Syrian city from ISIS, defeating the last militants who had been holding out in the de facto capital of their now-shattered caliphate.

The victory capped a battle of more than four months and hammered another nail in the coffin of the militant group's experiment in statehood, which has collapsed in the face of offensives in Syria and Iraq.

The SDF broke into Raqqa in June, after months of fighting to surround the city, and yesterday flushed out the last few hundred militant fighters from their remaining positions in the main hospital and the municipal stadium.

"Everything is finished in Raqqa - our forces have taken full control of the city," the alliance's spokes-man Talal Sello told Agence France-Presse.

The announcement came just days after the SDF said it was launching the final phase of its operation to retake the city.

The breakthrough in the operation, which was launched on June 6, came after a deal was struck allowing the evacuation in recent days of civilians who had been held as human shields.

News about Raqqa's liberation was overwhelming for former resident Umm Abdullah, who fled the city three years ago.

"I can't describe my happiness," the 44-year-old told AFP in the town of Kobane, 100km north of Raqqa. "When my sister told me it had been freed, she started to cry, and then I started to cry. Thank God, thank God."

The loss of Raqqa as well as the Iraqi city of Mosul in July "will certainly tarnish the group's aura of historic achievement for having created a modern caliphate, as they call it. They are now losers in a sense", said Mr Daniel Benjamin, who served as coordinator for counter-terrorism at the US State Department until 2012, and is now director of the John Sloan Dickey Centre for International Understanding at Dartmouth College.

"I don't think that should be underestimated. Symbols are vitally important," he said.

However, it is by no means the end of ISIS, he added, noting: "The group will inevitably revert to more traditional terrorist activity."

Analysts and diplomats also fear that the group will come back in a different guise.

The fight to dislodge ISIS has intensified the very problems that led to its rise in the first place.

In both Iraq and Syria, Sunni Muslims have been on the losing end of the civil wars that engulfed the countries - fuelling support for extremist groups.

In Syria especially, the forces that are driving out ISIS have often had few ties to the local population, leaving the way open for yet another cycle of disputes over land, resources and power.

Success or failure will hinge on how Raqqa's new rulers govern.

Mr Brett McGurk, United States special presidential envoy for the global coalition to counter ISIS, said in Washington in July that governance would be led by a 120-member civilian council that has been based in Ayn Issa, to the north of Raqqa.

The council has committed to holding an election in Raqqa by May next year for a new governing body to ensure that the people of the city can choose their own leaders, ahead of a final solution to the Syrian war, he said.

AGENCE FRANCE-PRESSE, BLOOMBERG