Iraqi armed forces launched an operation on Saturday to capture the last Daesh-held enclave in Mosul, according to a military statement.
The Iraqi air force dropped leaflets on Friday urging residents in the enclave to flee, raising fears among humanitarian groups for the safety of desperate civilians there.
The enclave covers mainly the Old City centre and three adjacent districts alongside the western bank of the Tigris river.
The fall of the city would, in effect, mark the end of the Iraqi half of the "caliphate" declared nearly three years ago by Daesh leader Abu Bakr al-Baghdadi, which also covers parts of Syria.
The U.S.-backed offensive in Mosul, now in its eighth month, has taken longer than planned as the militants are dug in among civilians.
"The joint forces have began liberating the remaining districts," an Iraqi military statement said.
Another military statement announced the death of two Iraqi colonels during the fighting on Saturday.
The push inside the Old City coincides with the start of the holy fasting month of Ramadan. The offensive's prime target is the medieval al-Nuri mosque with its landmark leaning minaret, where Daesh's black flag has been flying since mid-2014.
Iraqi armed forces hope to capture the mosque - where Baghdadi announced the "caliphate" - in the next few days.
The insurgents are also retreating in Syria, mainly in the face of U.S.-backed Kurdish-led forces.
The insurgency is expected to continue in the sparsely populated desert region along the Syrian border even if Mosul is fully captured.
Meanwhile, the United States has admitted that at least 105 Iraqi civilians were killed in an air strike it carried out in Mosul in March.
US Central Command (CentCom) said it had targeted two snipers from so-called Daesh with what it called a "precision-guided munition".
However, the strike detonated explosives that militants had placed in the building, CentCom said.
Civilians sheltering in the lower floors were killed when it collapsed.
The civilians had gathered in the lower floors of the building after being expelled from their homes by Daesh fighters, a declassified summary of the report said.
Those organising the strike "could not have predicted the presence of civilians in the structure prior to the engagement," it added.
US officials said the type of bomb was chosen "to minimise collateral damage," but the explosives hidden by Daesh were at least four times more powerful than the weapon itself.
"Our condolences go out to all those that were affected," Major General Joe Martin said in a statement.
"The coalition takes every feasible measure to protect civilians from harm."
Initial media reports had placed the casualty estimates as high as 200.
Hundreds of thousands of civilians have fled the northern Iraqi city as the operation to reclaim it has continued.
Thousands of Iraqi security forces, Kurdish Peshmerga fighters, Sunni Arab tribesmen and Shia militiamen, assisted by US-led coalition warplanes and military advisers, are involved in the offensive, which was launched in October 2016.
The government announced the full "liberation" of eastern Mosul in January 2017. But the west of the city has presented a more difficult challenge, with its narrow, winding streets.
Source: NAM News Network