A displaced man, who fled the Islamic State stronghold of Mosul, carries a woman in the Mithaq district of eastern Mosul, Iraq, January 3, 2017. [Photo/Agencies]

After quick initial advances, the operation stalled for several weeks but last Thursday Iraqi forces renewed their push from Mosul's east towards the Tigris River on three fronts.

Elite interior ministry troops were clearing the Mithaq district on Wednesday, after entering it on Tuesday when counterterrorism forces also retook an industrial zone.

Federal police advanced in the Wahda district, the military said on Wednesday, in the 12th week of Iraq's largest military campaign since the US-led invasion of 2003.

As they advanced, many more civilian casualties were also being recorded, the UN said.

Vastly outnumbered, the militants have embedded themselves among residents and are using the city terrain to their advantage, concealing car bombs in narrow alleys, posting snipers on tall buildings with civilians on lower floors, and making tunnels and surface-level passageways between buildings.

"We were very afraid," one Mithaq resident said.