ISIS extremist group’s militants accompanied by women and children surrendered to the Syrian Democratic Forces (SDF) in their hundreds on Thursday as the extremists lost ground to a US-backed assault on their last shred of territory, the SDF said.

Many of the men could be seen limping as they crossed out of the enclave at Baghouz along a dirt path over a rocky hill, accompanied by weeping children and fully veiled women, dragging suitcases and backpacks behind them.

Some of the men were wounded or on crutches. Many were believed to be foreign, SDF fighters said. Children were hoisted onto shoulders to get them up the hill, and strollers left behind.

SDF commander Adnan Afrin said the number of evacuees had yet to be determined as people were still emerging but it was in the hundreds, adding to the many thousands who have streamed out of Baghouz in recent weeks.

The surrender took place during a pause in the US-backed offensive that began on Sunday to seize the final patch of populated ISIS territory - which once spanned a third of Iraq and Syria, including the cities of Mosul and Raqqa.

Earlier, artillery fire had pounded the enclave as warplanes flew overhead.

The SDF said the extremists had deployed more than 20 suicide bombers in three counter-attacks in the last two days.

It said at least 112 militants had been killed since it resumed the assault, including more than 15 on Thursday morning.

No ISIS leaders are believed to be in Baghouz, according to a US defense official. US government experts strongly believe group leader Abu Bakr al-Baghdadi is alive and possibly hiding in Iraq.

The group is still assessed to be a potent security threat with a foothold in remote areas, and is widely expected to escalate a campaign of guerrilla attacks.