Iraqi forces engaged in fierce combat with Islamic State (IS) militants outside Mosul’s Old City on March 19 as they pressed forward in a bid to recapture the western part of the city.

Iraqi federal police and the elite Rapid Response Force continued their offensive on IS targets, including with rockets and mortar rounds, as they closed in on the important Al-Nuri Mosque in west Mosul.

Residents of the city continued to flee the area as the battle for the western part of the city moved into its second month.

"Federal Police and Rapid Response forces resumed their advance after halting operations due to bad weather. The troops have a target of retaking the rest of the Old City," a police spokesman was quoted by Reuters as saying on March 19.

The operation to recapture Mosul, the last IS stronghold in Iraq, was launched in October, with Iraqi forces backed by U.S. air support and artillery.

Government troops captured the eastern half of the militants' so-called capital in Iraq in January after 100 days of fighting, and the offensive to capture west Mosul was launched with U.S. air support on February 19.

U.S. officials have estimated as many as 750,000 civilians may have been in west Mosul at the start of the offensive, along with some 2,000 IS fighters.

According to United Nations figures, some 255,000 people have been displaced from Mosul and its outskirts since October. That figure includes some 100,000 displaced persons since the beginning of the operation to retake west Mosul last month, according to the UN.

IS militants have been fighting back with sniper fire, mortars, and armored suicide car bombs, officials say.

The extremist group's stronghold in Syria, Raqqa, is also under pressure from U.S.-backed forces.

IS militants seized large portions of northern Iraq and Syria in an offensive in 2014.

The group has been accused of numerous atrocities and has claimed responsibility for major terrorist attacks in Europe and elsewhere.