U.S.-backed Iraqi security forces closing in on the Islamic State-held western half of Mosul stormed the city's airport and a nearby military base on Thursday, state television said.

Counter-terrorism service (CTS) troops and elite interior ministry units known as Rapid Response descended on the airport early on Thursday and the nearby Ghozlani military complex, CTS spokesman Sabah al-Numan told state TV.

"Our forces started a major operation early this morning to storm the airport of Mosul and the Ghozlani base to dislodge Daesh (Islamic State) terrorists. We can confirm that the Mosul airport militarily has fallen and it’s a matter of short time to fully control it," Numan said.

After ousting the militant group from eastern Mosul last month, Iraqi forces have sought to capture the airport and use it as a launchpad for an onslaught into the west of Iraq's second-largest city.

The airport and military complex, which includes barracks and training grounds and sprawls across an area close to the Baghdad-Mosul highway was captured by Islamic State fighters when they overran Mosul in June 2014.

Loss of Mosul could spell the end of the Iraqi side of IS's self-styled caliphate, which it declared from the city after sweeping through vast areas of Iraq and Syria.

The campaign involves a 100,000-strong force of Iraqi troops, Kurdish fighters and Shi'ite militias.

Forces have made rapid advances since the start of the year, aided by new tactics and improved coordination, military officials say.