MOSUL, Iraq -- After weeks of unchanging front lines, the Iraqi army rolled Tuesday into a southeastern Mosul neighbourhood held by Islamic State militants, taking a hospital before meeting stiff resistance, the military said.

The push began just after 6 a.m. with a barrage of airstrikes that kicked up dark clouds of smoke in the modest al-Salam residential neighbourhood. The bombardment by Iraqi air support and the U.S.-led coalition appeared heavier than previous operations in the area.

Coalition forces providing logistical support could be seen about 4 kilometres (2.5 miles) from the front.

Iraqi troops also reported fewer car bombs than in previous assaults. After one such attack, at least two military vehicles could be seen carrying wounded from the front.

By evening, Iraqi forces had only secured a few hundred meters (yards) and clashes continued.

Thick plumes of smoke billowed from the hospital after the commander of a joint operations centre that oversees the Mosul campaign, Lt. Gen. Abdul-Amir Yarellah, pronounced the site retaken by the army's 9th Division.

"The hospital was a Daesh base," said Lt. Ahmed Abu Fadl, using the Arabic acronym for IS.

"They were treating their wounded there," he added, explaining that he hoped retaking the building would hurt their ability to launch counterattacks.

Units from the 9th Division slowly moved across the main road marking the front line in heavily armoured personnel carriers. As the convoy rolled through narrow streets on Mosul's edge, children waved and shouted from the tops of garden walls.

As the soldiers pushed deeper into the city, however, only a handful of families peered out at them from garden gates.

In a neighbourhood that was declared liberated weeks ago, sniper rounds sent advancing troops ducking for cover.

From the rooftop of Fathii Muhammad Yousef's two-story house, he pointed to a minaret where an IS sniper was firing.

"Starting before dawn, we heard more than 20 airstrikes," said Yousef, who took cover with his family of 10 in their home just a block from the front.

For the past month, Iraqi forces have clashed with IS fighters on the streets outside his home. Mortars and tank rounds have scarred its walls and broken its windows. Four of his neighbours have been wounded by gunfire and shrapnel, he said.

Yousef hopes Iraqi forces will push past his neighbourhood so his family will be able to have access to food and clean water. In the past week, he ran out of water and is now running low on food.

"All we have now is well water. It's not clean enough to drink, but what else can we do?" he said, adding that the water is making some of his children sick.

The campaign to retake Mosul began Oct. 17. Iraq's second-largest city, it is the last major IS urban bastion in the country.

While Iraqi forces on the eastern side of the city have made some of the largest gains, front lines on the south and southeast have barely moved for weeks as troops have struggled to reinforce their defensive lines.

In an audio recording published online, new IS spokesman Abu al-Hassan al-Muhajir urged the fighters in Mosul and in the Syrian city of Raqqa to keep up the fight and not retreat.

It was not clear when the nearly 30-minute recording was produced. It was distributed by the militant group's al-Furqan media arm late Monday night. Al-Muhajir replaced Abu Mohammed al-Adnani, who was killed in an August airstrike.

IS captured Mosul in 2014 along with nearly a third of Iraqi territory and large parts of neighbouring Syria. In the past year, Iraqi troops, federal police and allied Shiite and Sunni militias have pushed the militants from most of the vast Sunni province of Anbar, west of Baghdad, and areas to the north and east of the capital.

- Salaheddin reported from Baghdad. Associated Press writer Maamoun Youssef in Cairo contributed to this report.