Artillery and air strikes pounded the city, still home to 1.5 million people, and residents of the eastern neighbourhood of al-Quds said the ultra-hardline Sunni militants had resorted to street fighting to try to hold the army back.

Soldiers of the elite Counter Terrorism Service also entered the state television station in Mosul on Tuesday, the first capture of an important building in the Islamic State-held city since the start of the offensive about two weeks ago, the force commander, Lieutenant-General Talib Shaghati, said.

“This is a good sign for the people of Mosul because the battle to liberate Mosul has effectively begun,” Shaghati said.

Iraqi troops, security forces, Shi’ite militias and Kurdish peshmerga have been advancing on several fronts towards Mosul, backed by U.S.-led troops and air forces. Special forces units sweeping in from the east have made fastest progress.

“We are currently fighting battles on the eastern outskirts of Mosul,” CTS Lieutenant-General Abdul Wahab al-Saidi said. “The pressure is on all sides of the city to facilitate entry to the city centre.”

He said CTS forces had cleared Islamic State fighters from most of the eastern district of Kokjali, close to al-Quds, on Tuesday, “so now we are inside the district of Mosul”.