US-backed force defeat IS in their Syrian capital Raqqa

Talo Silo, a spokesman for the Syrian Democratic Forces, or SDF, said that military operations had halted and that members of the joint Kurdish-Arab force were clearing the city of explosive devices and hunting for sleeping cells.

It was still unclear whether some Islamic State pockets remained, but the SDF portrayed the battle for Raqqa as effectively over.

Besieged and severely weakened, dozens of militants had launched a final stand from inside Raqqa's main hospital and stadium. But hundreds of others surrendered during the final days of the battle after local officials brokered a controversial deal which could see many escape prosecution.

The offensive to recapture the city began in June, with the SDF advancing on foot as US-led coalition airstrikes pummeled the militants down below. Much of the city now lies in ruins, its residents scattered throughout displacement camps across the country.

By the time the battle was over, Raqqa had lost all strategic significance to the group that had once used the city to showcase its prowess and its brutality. The fall of Mosul in July and the loss of large areas of territory in eastern Syria to Syrian government forces leave the militants in control of just a few pockets of territory spanning the Iraqi Syrian border.

But the capture of the city by the US-backed Syrian Democratic Forces, backed by US airstrikes and US advisers on the ground, nonetheless marks a milestone in the US led effort to defeat the militants.

Raqqa was the first provincial capital to fully fall from government control when it was captured by a rebel army containing moderate and hard-line groups, including the al-Qaeda-linked Jabhat al-Nusra, in March 2013.

It established a civilian government but divided into factions two months later, with one renaming itself the Islamic State of Iraq and al-Sham, or ISIS.

After the city's Islamist militants swore loyalty to the group, it became their de facto capital, and by January of 2014, the extremists were firmly in control.

If the Iraqi city of Mosul gained notoriety as pulpit from which the Islamic State declared its religiously-inspired caliphate, Raqqa became the stage from which it showcased its form of rule. Residents were corralled to watch executions and other acts of ritual humiliation in its central square.

Raqqa's southern mountains provided the backdrop to perhaps the group's most famous execution of all — that of American journalist James Foley, dressed in an orange jumpsuit and forced to castigate President Obama's foreign policy before he was beheaded by a British militant, Mohammed al-Emwazi.

Known first to the world as "Jihadi John," the Kuwaiti-born fighter would go on to kill several more Western hostages before he died in a US drone strike on the city's central square. Three years after Raqqa's capture, the Islamic State's fortunes have changed drastically.