NEAR MOSUL, Iraq: Iraqi forces retook the provincial government headquarters and a second bridgehead on the River Tigris in west Mosul Tuesday, the third day of a new drive against ISIS.

The operation to retake west Mosul -- ISIS' largest remaining urban stronghold -- was launched on Feb. 19, but the advance had slowed in the face of several days of bad weather until a renewed push began Sunday.

"The heroes of the federal police and Rapid Response liberate the government building for Nineveh province and control the second bridge (Al-Hurriyah Bridge)," the Joint Operations Command said in a statement.

Mosul, Iraq's second city, is the capital of Nineveh province.

The city is divided by the Tigris River, and while bridges crossing it have been either damaged or destroyed, they would provide a link between the government-held east and ISIS-held west if they can be repaired or otherwise bridged.

British and U.S. military instructors have been training Iraqi soldiers in the use of floating bridges for precisely this kind of situation.

Iraq's Bridging Battalion currently numbers around 90 troops and a further 25 are completing training.

Iraqi forces have retaken a series of government buildings in west Mosul since launching their renewed offensive.

The elite Rapid Response Division and federal police forces have recaptured the provincial police headquarters, the courts complex and the water, electricity and sewage directorates.

And the Counter Terrorism Service, the country's premier special forces unit, retook Al-Sumood neighborhood, another target in the drive, and attacked Al-Mansur.

The fighting in west Mosul has forced more than 50,000 people to flee, the International Organization for Migration said.

The operation to retake Mosul was launched on Oct. 17, with an array of forces taking part but CTS and Rapid Response ultimately playing the leading roles.

In January, Iraqi forces retook the last neighborhood of east Mosul still in ISIS hands.

ISIS overran large areas north and west of Baghdad in 2014, but Iraqi forces backed by U.S.-led air strikes and other support have since regained most of the ground they lost.

The extremists have also lost larges swathes of territory in neighboring Syria, threatening the end of the cross-border "caliphate" they declared in June 2014.

They have faced offensives by three rival forces.

Turkish troops and their Syrian rebel allies have pushed south from the Turkish border and drove ISIS out of the northern town of Al-Bab.

Syrian government troops have pushed east from second city Aleppo with Russian support and seized a swathe of countryside from the extremists.

An a U.S.-backed alliance of Kurdish and Arab fighters have been advancing on ISIS' de facto Syrian capital Raqqa and Monday reached the Euphrates River cutting the main road to the partly ISIS-held city of Deir Ezzor downstream.