Iraqi forces make first push into Mosul

Iraqi forces have entered Mosul, as the battle to take back the city from Islamic State enters its third week.

Iraqi Shi'ite militias launch an offensive on Islamic State positions west of Mosul. (AAP) Source: AP

Advancing Iraqi troops have broken through Islamic State defence lines in an eastern suburb of Mosul, taking the battle for the insurgent stronghold to inside the city limits for the first time, a force commander says.

They made the gain as the offensive to recapture Mosul -- the largest military operation in Iraq since the US-led invasion that toppled Saddam Hussein in 2003 -- entered its third week.

Commanders had warned earlier that the battle for the city, the hardline militants' de facto capital in Iraq, could take weeks and possibly months.

Troops of the Iraqi army's Counter-Terrorism Service (CTS) moved forward on Gogjali, an industrial zone on the eastern outskirts, on Monday after two weeks of fighting to clear surrounding areas of the insurgents.

Source: AAP

The fighting ahead is likely to be more difficult as civilians still live there, unlike most villages taken so far by the Iraqi forces which were emptied of their Christian population.

Islamic State singled out religious minorities in northern Iraq, including Christians and Yazidis, for killing and eviction after leader Abu Bakr al-Baghdadi declared a caliphate in 2014 over territory they captured there and in neighbouring Syria.

Their seizure of Mosul and surrounding towns effectively drove Christians from the area for the first time in two millennia.

The recapture of Mosul would mark the militants' effective defeat in the Iraqi half of the territory they had seized.

It is still home to 1.5 million residents, making it four of five times bigger than any other city they controlled in both Iraq and Syria.

"The battle of Mosul will not be a picnic," Hadi al-Amiri, leader of the Badr Organisation, the largest Shi'ite militia fighting with Iraqi government forces, said from the southern frontline.

"We are prepared for the battle of Mosul even if it lasts for months."

Pro-Iranian Iraqi Shi'ite militias joined the fighting over the weekend, aiming to cut the route between Mosul and Raqqa, Islamic State's main stronghold in Syria.

They have also set oil wells on fire to cover their movements and displaced thousands of civilians from villages toward Mosul, using them as "human shields", UN officials and villagers have said.