GOGJALI, Iraq — Iraq’s special forces entered the outskirts of Mosul on Tuesday, taking the state television building and advancing despite fierce resistance by Islamic State group fighters who hold the city, an Iraqi general said.

It was the first time Iraqi troops have set foot in the city, Iraq’s second largest, in over two years. The advance could be the start of a grueling and slow operation for the troops, who will be forced to engage in difficult, house-to-house fighting in urban areas that is expected to take weeks, if not months.

Troops entered Gogjali, a neighborhood inside Mosul’s city limits, and by noon were only 800 meters (yards) from the more built-up Karama district, according to Maj. Gen. Sami al-Aridi of the Iraqi special forces.

“The special forces have stormed in,” he said. “Daesh is fighting back and have set up concrete blast walls to block off the Karama neighborhood and our troops’ advance,” he said, using the Arabic acronym for the Islamic State group. Bombs have been laid along the road into the city, he added.

Later, al-Aridi said the troops had taken the nearby state television building, the only one in the province, and that heavy fighting broke out when they tried to continue further in to built-up areas.

Mosul is the final IS urban bastion in Iraq, the city from which it drove out a larger but demoralized Iraqi army in 2014 and declared a “caliphate” that stretched into Syria. Its loss would be a major defeat for the jihadis, but with the closest Iraqi troops still some 10 kilometers (6 miles) from the city center, much ground remains to be covered.

Tuesday’s battle opened up with Iraqi artillery, tank and machine gun fire on IS positions on the edge of Gogjali neighborhood, with the extremists responding with guided anti-tank missiles and small arms in an attempt to block the advance. Airstrikes by the U.S.-led coalition supporting the operation added to the fire hitting the district.