There are signs that leaders from self-styled Islamic State (IS) have fled Mosul as Iraqi forces close in on the city, the US military says.
“Make no doubt the Iraqi security forces have the momentum,” Gen Gary Volesky said.
The Iraqi army has been moving towards Mosul from the south, while their Kurdish allies have been approaching from the east.
There are thought to be up to 5,000 IS fighters still in the city.
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“We’ve seen movement out of Mosul; we’ve got indications that leaders have left,” said Gen Volesky, giving his assessment of the situation.
But he did not specify who had fled, nor did he say where they had gone to.
The whereabouts of IS leader Abu Bakr al-Baghdadi are unknown. Some reports say he is in Mosul; others say he has fled the northern Iraqi city.
It is possible that any fighters leaving the city had simply been going to man front line areas, which still lie beyond the outskirts, the BBC’s Middle East analyst Alan Johnston says.
Nobody has any doubt that a hardcore of IS militants will stay in the city and fight for it, perhaps very fiercely indeed, our correspondent adds.
Gen Volesky, who heads the land component of the US-led coalition fighting IS, said that foreign fighters are likely to form the bulk of the force who will hold out.
“A lot of foreigner fighters we expect to stay, because they’re not going to be able to exfiltrate as easily some of the local fighters, or the local leadership, so we expect there to be a fight,” he said.
The charity Save the Children claims that 5,000 people from the conflict area have fled to a refugee camp over the border in Syria in the last 10 days, with another 1,000 waiting at the border.
Al-Hol was built to house 7,500 people but currently holds 9,000 refugees.
The camp is being expanded to eventually take in 50,000 people, but Save the Children says the camp currently has just 16 latrines, is littered with waste and faeces, and has no clean water.
Refugee camps are being built in the south, east and north of Mosul in preparation for a flood of people fleeing the city. The UN says it expects at least 200,000 in the coming days and weeks.
Up to 1.5 million civilians are thought to still be in Mosul, with those inside reporting that IS was preventing them from leaving and that they were running out of basic supplies.
Mosul has been in the hands of IS since 2014 and is the militants’ last major Iraqi stronghold.
The offensive to retake Mosul began on Monday,
with the advancing forces seizing a number of villages on the city’s outskirts ahead of a final push into the city.
But progress is expected to be slow, with IS fighters appearing to be putting up stiff resistance in places.
There are warnings the group could use human shields or chemical weapons.
It could be months before the city is liberated.