The UN Office for the Coordination of Humanitarian Affairs (OCHA) estimates that about 500,000 people remain in western Mosul neighbourhoods that are still under the control of Islamic State militants, including 400,000 in the densely populated old city.
Iraqi Federal Police forces "are engaged in hard, house-to-house clashes with ISIS fighters inside the Old City", a media officer from these units told Reuters.
Government forces, including army, police and elite counter terrorism units have taken back most of Mosul, including the half that lies east of the Tigris river.
Several predicted deadlines for victory have come and gone, and the fighting is now largely centered in the "Old City" area of western Mosul, which Iraqi troops arrived in about a month ago.
The militants are now surrounded in the northwestern quarter including the historic Old City, using booby traps, sniper and mortar fire against the assailants.
Food and water shortages continued in western Mosul in north Iraq, which has been cut off from its main supply route since November 2016, and remained largely inaccessible to aid workers, a United Nations spokesman said here Tuesday.
On Friday, the army dismantled makeshift bridges linking the two parts of Mosul due to heavy rain, forcing residents leaving Iraq's second-largest city to use small boats.
ISIS is talking to al-Qaeda about a possible alliance as Iraqi troops close in on ISIS fighters in Mosul, Iraqi vice president Ayad Allawi said in an interview on Monday.
Aid shipments also resumed to the Hammam al-Alil camp, southwest of Mosul, the main arrival point for people fleeing the fighting.
Since the start of military operations to retake Mosul six months ago, almost half a million people have been displaced from their homes. "There are discussions and dialogue between messengers representing ISIS leader Abu Bakr al-Baghdadi and representing al-Qaeda leader Ayman al-Zawahiri".
The mosque is a symbolic site for the terror group.
It is unclear how exactly the two group may work together, Allawi said.