The Iraqi forces said they launched new assaults in Mosul's Old City on Monday after more than two weeks of only small advances and a high civilian death toll, according to a Reuters report.

The onslaught to oust Daesh from its last major Iraq stronghold has since October recaptured the whole east side of Mosul and half of the west, which contains the ancient quarter from where Daesh proclaimed its caliphate spanning large tracts of Iraq and Syria in 2014.

The civilian death toll has increased in the more densely-populated west of Mosul as the militants have used homes for cover, drawing air strikes that have killed residents, reports Reuters.

Iraqi forces have discussed new tactics, which a U.S military official said might include opening a second front and trying to isolate the Old City.

"Federal police and Rapid Response units started to advance in the southwestern part of the Old City" towards the al-Nuri mosque area, the police said in a statement on Monday.

Iraq's federal police chief, Lieutenant General Raed Shakir Jawdat, said new advances, supported by air power, were being aided by "precise targeting of selected positions" provided by intelligence.

"Our advance aim is to protect civilian lives, infrastructure and private properties," he was quoted by state TV as saying.

Another federal police officer said the attacks were "the start of the operations to seal off the Old City and prevent Daesh from receiving reinforcements and fleeing".

The objective, he said, was to "tighten the noose" around Daesh.