BAGHDAD — Iraqi troops fired automatic weapons at positions held by the Islamic State group in and around the northern city of Mosul on Thursday, but did not advance as they regroup and clear neighborhoods once occupied by the jihadis.

In Mosul proper, where troops have a foothold in a sliver of territory in the city’s east, the special forces control the Zahra neighborhood, once named after former dictator Saddam Hussein, military officials said.

They have taken at least half of the Aden neighborhood and clashes were still ongoing there, while the regular army’s ninth division is stationed in east Mosul’s Intisar neighborhood, they added, speaking on condition of anonymity because they weren’t authorized to brief reporters. Skirmishes also continued in the city’s southern outskirts.

Col. John Dorrian, a spokesman for the U.S.-led forces operating the key air campaign against IS, said that advancing troops and aircraft have destroyed some 70 tunnels the jihadis had been using to launch surprise attacks from inside densely populated areas.

“They’ve set up elaborate defenses, and we have to assume they’ll do anything among the civilian population because they don’t care about anyone,” he said, noting that airstrikes had hit hundreds of IS positions in the three-week old Mosul campaign.

Iraqi troops are converging from several fronts on Mosul, the country’s second largest city and the last major IS holdout in Iraq. Kurdish peshmerga forces are holding a line outside the city in the north, while Iraqi army and militarized police units approach from the south, and government-sanctioned Shiite militias are guarding the western approaches.