Talks on the safe exit of civilians trapped in Syria's Raqa were under way Wednesday, as US-backed forces prepare a final push to recapture the city from the Islamic State group.

The Syrian Democratic Forces, an alliance of Kurdish and Arab fighters, have taken around 90 percent of the city from IS since they broke into it in June.

The US-backed militia has surrounded remaining IS fighters in just a handful of positions, but thousands of civilians are still in the city, some of them being used as human shields by the jihadists.

Late Tuesday, the US-led coalition said officials from the Raqa Civil Council -- a provisional administration for the city set up by the SDF -- were trying to negotiate the safe passage of civilians from remaining IS-held areas.

"The Raqa Civil Council is leading discussions to determine the best way to enable civilians trapped by Daesh to exit the city, where some are being held as human shields by the terrorists," the coalition said, using the Arabic acronym for IS.

"Those departing Raqa who are found to have fought for Daesh will be turned over to local authorities to face justice."

The RCC declined comment on the discussions.

The Syrian Observatory for Human Rights, a Britain-based monitor of the war, said the talks were focused on granting surrendering IS fighters and their families a way out of Raqa.

"The negotiations are for the exit of Daesh fighters and their families to Albu Kamal and eastern Deir Ezzor province," said Observatory director Rami Abdel Rahman.

Albu Kamal is on the Syrian border with Iraq, and the town and adjacent areas in the east of Deir Ezzor province remain under IS control.

Deals to allow IS fighters to withdraw from territory have been negotiated in the past, including in May when an agreement allowed several dozen jihadists to flee the town of Tabqa, west of Raqa.

IS fighters and their families were also allowed to leave parts of the border region between Lebanon and Syria earlier this year, headed for Deir Ezzor, in a controversial deal agreed by the Syrian government and its Lebanese ally Hezbollah that was fiercely opposed by the US-led coalition.

- 'Lasting defeat' -

"We have a responsibility to defeat Daesh while preserving civilian life to the greatest extent possible," the coalition's director of operations, Brigadier General Jonathan Braga, said in a statement on Tuesday.

"Make no mistake: a lot of hard fighting remains and we are committed to the lasting defeat of Daesh."

Jihan Sheikh Ahmed, spokeswoman for the SDF's offensive, told AFP that between 600 and 700 active IS fighters were believed to remain in Raqa, with an additional 800 to 900 wounded jihadists also still inside the city.

The UN estimates that up to 8,000 people may still be in Raqa, although each day groups ranging from a dozen to several hundred people escape towards the SDF.

Coalition spokesman Colonel Ryan Dillon wrote on his Twitter account that more than 400 civilians had escaped on Tuesday.

"ISIS so-called capital slipping away," he wrote, using an alternative acronym for the jihadist group.

On Wednesday morning, SDF fighters in the city contacted by AFP reported that the fronts were mostly quiet, although there were sporadic air strikes by the US-led coalition.

The coalition's strike releases also showed the number of its air raids on Raqa dropping in the past two days from dozens a day to fewer than 10.

The SDF has been advancing on remaining IS-held territory from two fronts in the city's north and east, and is expecting to enter the final week of the campaign when the two fronts meet up.

Raqa became the de facto Syrian capital of the Islamic State group's self-proclaimed "caliphate" straddling Iraq and Syria, and gained international infamy for the gruesome acts of violence the jihadists perpetrated there.

Its loss would leave IS with only a handful of remaining strongholds in Syria, mostly in Deir Ezzor province.

In Iraq, it has been ousted from nearly all of its territory, except for a stetch of the Euphrates Valley along the border with Syria.

Source: AFP