Iraqi army units advanced from southeast Mosul towards a bridge across the Tigris in the city center on Tuesday, in an attack that could give fresh impetus to the hard fought, seven-week battle for Islamic State's northern Iraq stronghold.

 

Campaign commander Lieutenant General Abdul Ameer Rasheed Yarallah was quoted by Iraqi television as saying troops had entered Salam Hospital, less than a mile (1.5 km) from the Tigris river running through the center of Mosul.

 

If confirmed, that would mark a significant advance by the army's Ninth Armoured Division, which had been tied up for more than a month in deadly, close-quarter combat with Islamic State fighters on the southeast edges of the city.

 

A colonel in the armored division said Tuesday's assault, launched at 6 a.m., aimed to push towards the river and ultimately reach Mosul's Fourth Bridge, the southernmost of the five bridges spanning the Tigris which splits the city in two.

 

The bridge, like three others, has been hit by U.S.-led air strikes to prevent Islamic State sending reinforcements and suicide car bombs across the city to the eastern front, where counter-terrorism troops have spearheaded the army campaign.

 

The last and oldest bridge, built of iron in the 1930s, was targeted on Monday night, two residents said. The structure was not destroyed, but the air strikes made two large craters in the approach roads on both sides.

 

Militants immediately began to fill the craters, the residents told Reuters by telephone.

 

"I saw Daesh using bulldozers to fill the craters with sand and by midday vehicles managed to cross the bridge normally. I drove my car to the other side of the bridge and saw also Daesh vehicles crossing," said a taxi driver.

 

Mosul is by far the largest city under Islamic State control and defeating its fighters there would roll back the self-styled caliphate it declared in Iraq and Syria 2014 after seizing large parts of both countries.

 

Some 100,000 Iraqi soldiers, security forces, Kurdish peshmerga fighters and mainly Shi'ite paramilitary forces are participating in the overall Mosul campaign that began on Oct. 17, with air and ground support from a U.S.-led coalition.

 

Although it has made advances inside eastern Mosul, the army says it is battling the toughest urban warfare imaginable - facing hundreds of suicide car bomb attacks, mortar barrages, sniper fire and ambushes launched from a network of tunnels.

 

Its advance has also been slowed by the presence of more than 1 million residents in the city.

 

NEW TACTICS

 

The army colonel said Tuesday's offensive aimed to overwhelm the militants, who have put up stiff resistance but are hugely outnumbered by the attacking forces.

 

"We are using a new tactic - increasing the numbers of advancing forces and also attacking from multiple fronts to take the initiative and prevent Daesh fighters from organising any counter-attacks," the colonel said by telephone.

 

He said the four armored division regiments, whose tanks and heavy armour have struggled to adapt to street-by-street fighting, had been reinforced by an infantry regiment.

 

They were aiming for the Wahda neighborhood, a sprawling southeastern district that extends some distance into the city. Wahda could serve as a launchpad for an attack on the Fourth Bridge, he said.

 

It was not immediately possible to confirm whether troops had reached Salam hospital, deep inside Wahda neighborhood, but one person in Mosul contacted by telephone said he had heard from other residents that the army had advanced close to it.

 

The army push in the southeast comes as federal police units stationed west of the Tigris prepare a separate advance towards the airport on the southwestern edge of the city.

 

Residents have reported mortar fire and increased air strikes in the western half of the city, possibly in advance of a land offensive that would open up another front in the city and further stretch Islamic State defences.

 

The Sunni Muslim jihadists, who seized Mosul in mid-2014, are believed to be dug in across the city, but a U.S. general in the coalition supporting Iraqi forces told Reuters they appeared to have committed additional defences to the fight in the east.

 

Brigadier General Scott Efflandt said the coalition had expected the main defences to be in the west of the city, which is more densely populated and has a greater concentration of Sunni Muslims than the eastern section.

 

"What we thought was going to be the strongest defence, now they have already hedged their bets and brought it forward," said Efflandt, a coalition deputy commanding general.

 

"The quality of the enemy we are facing now is markedly declined from a month ago ... what they were saving for the west side of the river they are now committing to the east."

 

Echoing comments from Iraqi officers, he said the rate of suicide car bombings - which stand at a total of over 650 so far, according to the army - had dropped off recently.

 

He also said that the number of militants in the city had probably fallen to around 3,000, from around 3,000 to 5,000 at the start of the campaign.

 

Iraq officials have not given any casualty figures for their own forces. Last week the United Nations said nearly 2,000 members of Iraq's security forces had been killed in November - a figure Baghdad says was based on unverified reports - and that more than 900 police and civilians had also been killed.