Raqa, Syria, — US-backed forces said Tuesday they had retaken the main hospital in Syria's Raqa from the Daesh (the so-called IS) group and raised a militia flag inside Raqa stadium on Tuesday, one of the last remaining areas that were held by Daesh in its former capital.

The flag of the Kurdish YPG, the strongest of the militias in the Syrian Democratic Forces (SDF), was planted in the middle of the stadium, where fighting had ended, but which had not been fully cleared of landmines, militia fighters told the witness.

The capture of the state hospital brought the Syrian Democratic Forces closer to completing their conquest of Raqa, a northern city that was once the de facto capital of IS-held territory.

"The national hospital was liberated and... 22 foreign mercenaries were killed," the SDF said.

The militants also suffered setbacks Tuesday in the eastern Syrian region of Deir Ezzor, where Russian-backed regime forces retook swathes of territory, further reducing a "caliphate" that three years ago was roughly the size of Britain.

In Raqa, only about 300 IS fighters, mostly foreigners, were believed to remain in the last neighborhoods still out of the control of the SDF, a Kurdish-Arab alliance supported by the US-led coalition battling IS in Syria and Iraq.

The retaking of the hospital followed Monday's seizure by the SDF of an infamous roundabout used by the militants for public beheadings and crucifixions.

The Al-Naim traffic circle had been dubbed the "Roundabout of Hell" by residents under IS's more than three years of rule over the city.

As the sun was setting over Raqa's west Monday, a group of fighters gathered for the dabkeh — the jumpy line dance traditional in the Middle East — to celebrate their native city's near-recapture.

Three months after Iraqi forces retook Iraq's Mosul, the largest city the militant group controlled, the loss of Raqa will be another nail in the coffin of IS's brutal experiment in statehood.

The breakthrough in the operation to retake Raqa, 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.

Under the deal, a total of 275 Syrian IS fighters and relatives also surrendered to the SDF, though it was unclear whether they would be given safe passage elsewhere.

The final phase of the Raqa battle was launched on Sunday after a last batch of haggard-looking civilians was able to escape the devastated city.

The SDF said it may achieve full victory in Raqa very soon, but stressed that fierce fighting was still under way near the stadium.

"The end of the battle is fast approaching, maybe today or tomorrow," SDF spokesman Talal Sello told AFP.

After IS captured Raqa in 2014, the city become synonymous with the militant group's worst abuses and was transformed into a planning center for attacks abroad.

After Raqa, anti-IS efforts will focus on Deir Ezzor province, where the militants still control areas around the town of Mayadeen, part of provincial capital Deir Ezzor, as well as several villages and remote desert areas.

The Syrian Observatory for Human Rights said Tuesday that regime forces had brought the entire area stretching between Deir Ezzor and Mayadeen under their control following a major military offensive.

"These are not desert areas, they are villages along the Euphrates (river) that were IS strongholds," the Britain-based monitoring group said.

"The Daesh group is collapsing under pressure from the regime in Deir Ezzor province," it said.

IS also controls territory in neighboring regions on the Iraqi side of the border, where they are facing another US-backed offensive by Iraqi pro-government forces. — Agencies