US-led coalition warplanes have struck Islamic State's last stronghold in eastern Syria and hundreds of civilians fled the besieged enclave as US-backed fighters pressed their campaign to seize it.
Coalition jets roared overhead on Monday as columns of white smoke rose from the Islamic State-held Baghouz area a short distance from the Iraqi border, a Reuters witness said.
The Syrian Democratic Forces (SDF), which have driven Islamic State (IS) from swathes of northern and eastern Syria with US-led coalition support, launched an offensive on Saturday to capture the enclave in Deir al-Zor province.
The jihadists are putting up stiff resistance and had sought to counter-attack again on Monday morning, according to Mustafa Bali, head of the SDF media office. Around 1500 civilians had fled the enclave on Monday, he added.
SDF combatants watched as a column of at least 17 trucks filled with men, women and children left Baghouz and headed into SDF-held territory.
Some of those fleeing identified themselves as Iraqis.
"It seems there are still many civilians inside Baghouz," Bali said. "We are compelled to go cautiously and accurately in this battle."
On the outskirts of Baghouz, the people who had left stood in lines to be questioned by coalition and SDF forces apparently trying to identify whether any were jihadists.
Ahead of launching the attack, the SDF said more than 20,000 civilians had left Baghouz in the preceeding 10 days.
The SDF believes 400 to 600 jihadists may be holed up there, including foreigners and other hardened militants.
The SDF, which is spearheaded by the Kurdish YPG militia, advanced southwards into Deir al-Zor province after capturing Raqqa.
To the west of the Euphrates, in territory otherwise held by the Syrian government and its allies, Islamic State retains a foothold in mountainous terrain.
US President Donald Trump said in December he was pulling all 2000 US troops out of Syria, saying the battle against Islamic State there was almost won.
The top US commander overseeing American forces in the Middle East said on Sunday that the United States is likely just weeks away from starting the withdrawal.
Islamic State is still widely seen as a threat, however.
A top US general said last week IS would be an enduring menace following the US withdrawal, as it retained leaders, fighters, facilitators and resources that would fuel further insurgency.