Iraqi forces say they have retaken the main government offices in Mosul as the offensive continues to oust the so-called Islamic State (IS) group.

The advance could pave the way for an attack on the heavily-populated old city, where the militants are still entrenched.

Thousands of civilians are streaming out of the city every day.

Mosul is the last stronghold for IS in Iraq. The east of the city was recaptured in January.

Civilians said it was the heaviest night of bombardment since the operation to retake the city’s west began on 19 February.

The Iraqi forces launched a surprise attack overnight to storm the government buildings.

Although the structures are reported to be largely destroyed, they are a strategic and symbolic win.

Iraqi Prime Minister Haider al-Abadi arrived in Mosul on Tuesday morning to meet military leaders.

Iraqi forces ‘surrounded’

IS is fighting fiercely to retain its territory.

Sgt Azam Ibrahim of the federal police told The Associated Press news agency that his unit were among the first to storm the government office, but were then told to pull back amid fierce clashes.

“We were pulled back because we had killed and wounded,'” said Sgt Ibrahim. “The [Iraqi] forces there are surrounded, the Humvees [military vehicles] cannot reach them, nor can the ambulances.”

Iraqi forces have also captured the museum, the central bank’s main branch, which was looted by IS when they took over the city in 2014, and the nearby courthouse.

The court was used by IS to deliver harsh sentences, including stonings, throwing people off rooftops and chopping off hands, according to Reuters news agency.

The city’s museum has also been ransacked. Footage of IS fighters attacking ancient statutes with sledgehammers and drills emerged in February 2015.

One of the militants in the video described the artefacts as “false idols” and attempted to justify their destruction in religious terms.

On Sunday, Iraqi forces began a new push into the western part of Mosul after bad weather slowed them down.

The following day, they captured the al-Hurriya (Freedom) Bridge over the River Tigris.

They had already taken another bridge further south.

US-led airstrikes disabled all five of the city’s bridges last year.

The UN estimates that there are up to 800,000 people still living in west Mosul.

The organisation’s Office for the Coordination of Humanitarian Affairs says approximately 42,000 people were displaced last week alone.

“Given the narrow streets and high population density in western Mosul city, civilians are at great risk of being caught in crossfire, and infrastructure is likely to sustain damage. Clean drinking water is also in very short supply,” it said in a report released on Sunday.