NEAR BAGHOUZ, Syria - Syrian fighters backed by artillery fire from a US-led coalition battled a fierce jihadist counteroffensive Monday as they pushed to retake a last morsel of territory from the Islamic State group.
A war monitor said a coalition air strike killed 16 civilians including seven children trying to flee the holdout on Monday, but the US-led alliance was not immediately available for comment.
More than four years after the extremists declared a "caliphate" across large parts of Syria and neighboring Iraq, several offensives have whittled that down to a tiny holdout.
The Kurdish-led Syrian Democratic Forces on Saturday announced the final push to expel hundreds of diehard jihadists from that patch in eastern Syria on the Iraq border.
The US-led coalition maintained a steady beat of bombings on the last IS pocket on Monday, as the SDF faced fierce resistance.
The Syrian Observatory for Human Rights, a Britain-based war monitor, said 12 SDF fighters and 19 jihadists were killed in the fighting Monday.
"Heavy clashes are ongoing to pressure IS into surrendering," Observatory chief Rami Abdel Rahman said.
SDF spokesman Mustafa Bali said the SDF responded after IS launched a counterattack earlier in the day.
"IS launched a counterattack on our forces and we are now responding with rockets, air strikes and direct clashes," Bali told AFP earlier.
The sound of bombs echoed dozens of kilometres (miles) away and columns of dark grey smoke could be seen from SDF territory.
Bali said there were "dozens of SDF hostages held by IS" inside their last foothold, but denied reports of executions.
Backed by coalition air strikes, the SDF alliance has been battling to oust the jihadists from the eastern province of Deir Ezzor since September.
Since December, tens of thousands of people, most women and children related to IS fighters, have fled the shrinking jihadist holdout into SDF territory.
US-backed forces have screened the new arrivals, weeding out potential jihadists for questioning.
On Monday, dozens of coalition and SDF fighters were stationed at a screening point for new arrivals from IS areas.
Coalition forces stood over about 20 men who were crouching on the ground.
Two French women told AFP they paid smugglers to take them out of the battered IS-held holdout of Baghouz, but Iraqi jihadists had prevented other foreigners from leaving.
"They said only the Syrians and Iraqis can be smuggled out," said one of the women, who said her first name was Christelle, from the city of Bordeaux.
The Observatory said 600 people including around 20 suspected jihadists fled IS areas overnight.
The SDF said it advanced inside the pocket on Sunday, seizing 40 positions from IS.
On Saturday, the alliance said up to 600 jihadists as well as hundreds of civilians could remain inside the IS patch of 4 square kilometers (one square mile).
Spokesman Bali said IS leader Abu Bakr al-Baghdadi, the man who pronounced the cross-border "caliphate" in 2014, was not among them, and likely not in Syria.
PLANNED US WITHDRAWAL
At the height of their rule, the jihadists imposed their brutal interpretation of Islamic law on a territory roughly the size of Britain.
But military offensives in both countries, including by the SDF, have since retaken the vast bulk of their territory.
The jihadists however retain a presence in Syria's vast Badia desert, and have claimed a series of deadly attacks in SDF-held areas.
US President Donald Trump in December shocked Washington's allies by announcing a full withdrawal of US troops from Syria as IS had been "beaten".
But the US military warned in a report published this month that IS "could likely resurge in Syria within six to twelve months and regain limited territory" if sustained pressure is not maintained.
Trump's decision to withdraw US troops has left Syria's Kurds scrambling for safeguards.
A US departure makes them more vulnerable to a long threatened attack by neighboring Turkey, who considers Kurdish fighters to be "terrorists", and dashes their dreams of autonomy.
The Kurds have largely stayed out of Syria's nearly eight-year civil war, instead building their own semi-autonomous institutions in the northeast of the country.
But the expected US pullout has seen them grappling to mend ties with the Damascus regime, which is against Kurdish self-rule.
Syria's war has killed 360,00 people and displaced millions since it started in 2011 with the brutal repression of anti-government protests.