Iraqi troops on Thursday drove Islamic State militants from three more neighborhoods in the northern city of Mosul, pushing toward the city center in a slow, street-to-street fight that's now in its sixth week, according to a senior Iraqi commander.

Brig. Gen. Haider Fadhil of the special forces told The Associated Press that his men have retaken the neighborhoods of Amn, Qahira and Green Apartments and were expanding their foothold in the densely populated district of Zohour.

The neighborhoods are all in the eastern sector of Mosul, east of the Tigris River, where most of the fighting has taken place since the government's campaign to liberate the city began Oct. 17.

Government troops are backed by U.S.-led coalition airstrikes against IS positions in the city.

Mosul, captured by IS in 2014, is the last major urban center still held by the Sunni extremist group in Iraq.

Late Wednesday, a spokesman for one of the larger state-sanctioned Shiite militias fighting on the ground near Mosul said the militiamen have seized a road to the northwest of Mosul linking the city to Raqqa, the de facto capital of the IS group's self-styled caliphate in neighboring Syria. The militias have been converging on Tal Afar, an IS-held town west of Mosul that had a Shiite majority before falling to the extremists in 2014.

"We have cut off Tal Afar from Mosul and we cut off Mosul from Syria," Jaafar al-Husseini, a spokesman for the Hezbollah Brigades, told the AP.

Also Wednesday, a pre-dawn airstrike by the U.S.-led coalition struck a bridge across the Tigris River, which divides the city in two, leaving only one bridge for cars functioning in the city and disrupting IS supply lines.

It was the second bridge to be struck this week, and two other bridges were destroyed by airstrikes last month.