NIMRUD, Iraq — Heavy fighting broke out in Mosul’s eastern Tahrir neighborhood on Wednesday, where Iraqi special forces said a suicide car bomber from the Islamic State group disabled an Abrams tank belonging to the Iraqi army.

Backed by U.S.-led airstrikes but under fire from heavy weapons, the troops drove deeper into the neighborhood as families fled their homes. IS-fired mortar rounds killed a child and wounded five others, according to Rudaw TV, which ran footage of their evacuation by Iraqi troops.

Iraqi forces launched a long-awaited operation to retake the country’s second largest city nearly a month ago, but have only advanced into a few eastern districts. They have faced fierce resistance, with snipers, mortar fire and waves of suicide attackers driving armor-plated vehicles packed with explosives.

Brig. Gen. Haider Fadhil says the special forces now control 70 percent of the Tahrir district, where most residents are sheltering indoors. The army is trying to evacuate them as it battles street by street. Mosul is still home to more than 1 million civilians.

“Our forces have killed dozens of Daesh fighters, and we’re advancing carefully because of the civilians, who we’re evacuating,” Fadhil said, using the Arabic acronym for the extremist group.

In the same district, security forces arrested four IS militants, two Iraqis and two Arab foreign fighters, and locked them in a Humvee, bound and blindfolded.

To the west of Mosul, a state-sanctioned Shiite militia taking part in the operation to retake the northern city advanced toward Tal Afar, a town to the west that had a Shiite majority before it fell to IS in 2014.

Hezbollah Brigades spokesman Jaafar al-Husseini said fierce clashes were underway outside the Tal Afar military airport, without elaborating.

The Lebanon-based Al-Mayadeen TV broadcast footage showing thick black smoke rising from the airport as armored vehicles and troops were seen deploying nearby. The troops were also seen blowing up a speeding suicide car bomb before its driver managed to detonate his explosives.

Away from the front lines, Iraqi forces on Wednesday assessed the damage to the ancient site of Nimrud, a town some 19 miles (30 kilometers) southeast of Mosul. Iraqi troops entered Nimrud on Sunday in what was the most significant gain in several days for government forces.

Maj. Gen. Dhiaa al-Saadi said IS has almost completely destroyed the town’s ancient Assyrian archaeological site, and that he expects to find more damage to heritage sites as the operation continues. IS believes ancient ruins encourage polytheism.