The Syrian Democratic Forces and its allies from the US-led coalition unleashed a deluge of fire on the village of Baghouz at the weekend to break the defences of Islamic State group fighters in the final sliver of their "caliphate".

But the Kurdish-led force said their offensive had been slowed down Monday due to remaining civilians inside the pocket, and an SDF spokeswoman said hundreds had been evacuated out of the crumbling bastion in the past 48 hours.

"More than 800 people exited Baghouz from yesterday until today -- IS family members and fighters who surrendered," she said.

Through binoculars from an SDF position outside the jihadist holdout, an AFP correspondent saw men kneeling on the ground before boarding trucks, as well as women clad in black and children.

The push on IS's last pocket of territory had resumed Friday after days of mass evacuations, but SDF spokesman Mustefa Bali said Monday the operation was being hampered by the presence of more civilians in the besieged enclave.

"We're slowing down the offensive in Baghouz due to a small number of civilians held as human shields," he said.

Two SDF flags floated in the wind on a hill seized from the jihadists.

Three air strikes hit the village of Baghouz earlier in the day, causing a huge cloud of grey and black smoke to billow up into the sky.

- Air strikes -

An AFP reporter at the Omar oil field, one of the main staging areas for the assault, earlier in the day saw empty trucks heading towards the front line likely to ferry out more rescued civilians.

Despite being hugely outnumbered, jihadists making a desperate last stand in the riverside hamlet -- most of them foreigners according to the SDF -- are putting up stiff resistance.

They are using snipers, a network of tunnels, and suicide bombers to fight back.

On Sunday, eight suicide attackers blew themselves up before reaching SDF positions and three car bombs detonated at a distance, the Kurdish-led forces said.

SDF officers perched on rooftops have been receiving information on IS positions from elite units, and passing them on to the coalition to call in air strikes.

IS has lost several of its positions in such strikes since Friday in Baghouz, a village nestled in a palm-lined bend of the Euphrates River.

Seven SDF members and 18 jihadists have been killed in the fighting since the final push started, the Syrian Observatory for Human Rights says.

The capture of Baghouz would mark the end of IS territorial control in the region and deal a death blow to the "caliphate" proclaimed in 2014, which once covered huge swathes of Syria and Iraq.

At its peak more than four years ago, the proto-state created by IS was the size of the United Kingdom and administered millions of people.

It minted its own currency, levied taxes, and designed its own school curricula.

The "caliphate" effectively collapsed in 2017 when IS lost most of its major cities in both countries.

- US-Russia meeting -

The loss of Baghouz, which the SDF says is only days away, would carry mostly symbolic value.

The latest military operation has nonetheless sparked a major humanitarian emergency, with thousands of people of various nationalities emerging from the ruins of the "caliphate" and washing up in Kurdish-run camps.

The SDF, who launched a broad operation against the jihadists' last bastions in the Euphrates Valley in September, had earlier said they evacuated the last batch of civilians Friday.

But the families of several French jihadists contacted in France by AFP said Sunday that women and children remained inside.

After months under heavy bombardment and sometimes with very little to eat, families emerging from Baghouz are often in poor physical and psychological health.

The foreigners among them are not wanted in their countries of origin, and locals are filling camps that the Kurdish administration in the region says it needs more international help to run.

The US and Russian military chiefs were to meet on Monday to discuss operations in Syria, where Moscow has helped the Damascus regime regain large swathes of the country since a military intervention in 2015.

The United States is to keep a residual force in Syria after any declared victory against IS.

Almost eight years into a civil war that has killed more than 360,000 people and displaced millions, Damascus is back in control of nearly two-thirds of the country.