BAGHDAD: Up to 200,000 civilians caught between fanatical extremists and advancing Iraqi forces are in grave danger in the final stages of the battle for Mosul, a senior UN official said Monday.

More than seven months into the massive operation to recapture Mosul from ISIS, Iraqi forces have retaken the city's east and large parts of its western side, but the extremists are putting up tough resistance in areas they still hold.

"We are deeply concerned that right now, in the last final stages of the campaign to retake Mosul, that the civilians... in (ISIS) areas are probably at graver risk now than at any other stage of the campaign," Lise Grande, the UN's humanitarian coordinator in Iraq, told AFP.

Grande said that the UN estimates there are between 180,000 and 200,000 civilians in extremist-held areas of Mosul, the majority of them in the Old City area.

Iraqi aircraft have dropped leaflets over Mosul calling on civilians to leave and move towards security forces, which may push more civilians to flee.

"In the past several weeks, 160,000 civilians have fled, and our expectation is that, because of this order (from the government), we could be seeing a similar number of civilians flee in coming days," Grande said.

"Altogether, since the start of Mosul, 760,000 civilians have left their homes, and we are looking at the possibility of another 200,000 civilians leaving," she said.

Of the 760,000 civilians who have fled, some 150,000 have since returned home, leaving more than 600,000 currently displaced.

According to reports from families who have managed to flee, conditions in ISIS-held Mosul are increasingly dire.

"We understand that medicines are very scarce, that there are severe shortages of safe drinking water, that there are very limited stocks of food. We also are aware that families which try to escape are often targeted by snipers," Grande said.

"You have an enclosed area, you have fighters which are determined to hold out, the civilians are in many ways trapped in that area, there haven't been resupplies into the Old City for months," she said.

"You add all of that up and we are looking at a very desperate situation."