So-called Islamic State fighters are facing defeat in their last enclave in Syria (Picture: Islamic State).
The US-backed Syrian Democratic Forces say 3,000 Islamic State fighters and their families surrendered on Tuesday in their last small Syrian enclave of Baghouz.
It comes after three days of air strikes.
The SDF say a final assault will be launched against the last remaining few hundred fighters thought to be entrenched, once everyone who wants to surrender has done so.
Islamic State militants have called on supporters across the world to stage attacks in their defence, according to a newly released audio recording.
The recording, purportedly from IS, came as the Kurdish-led Syrian Democratic Forces faced continued resistance from IS gunmen as US-backed fighters try to push deeper into the village of Baghouz on the eastern bank of the Euphrates River.
The brief, minute-and-a-half recording, released by IS supporters on social media and reported by the SITE Intelligence Group, said that men, women and children in Baghouz are being subjected to a "holocaust by the Crusaders".
In the audio, an unidentified IS militant calls on Muslim "brothers, in Europe and in the whole world" to "rise against the Crusaders and ... take revenge for your religion".
As the man speaks, cracks of gunfire can be heard in the background, apparently meant to suggest that he is in Baghouz.
"Crusaders' warplanes" and "Kurdish atheists" are attacking his people, the man says.
The recording's authenticity could not be independently verified.
The capture of Baghouz would be a milestone in the devastating four-year campaign to defeat IS's so-called caliphate, which once covered a vast territory straddling Syria and Iraq.
On the ground, commanders said they have been hindered by IS sniper fire, but are relying more on air strikes and heavy weaponry, rather than ground forces.
Argish al-Deiri, an SDF commander in Baghouz, on Tuesday said IS militants had been fighting back with heavy weapons, rifles and sniper fire, forcing SDF fighters to slow their advance rather than advancing quickly so that "you don't lose your men".
He said he hoped the IS fighters will surrender in the coming "few days".