With an ISIS flag on the wall and remnants of equipment bearing testimony to the jihadists' quick flight, this is the inside of a base where foreign fighters were trained to kill.

Would-be terrorists could only enter the fortified base by crawling through a tunnel.

It was discovered by the Iraqi army in the south of Mosul, which had been under ISIS control since 2014.

The underground base was discovered by the Iraqi army in the south of Mosul, which had been under ISIS control since 2014

A member of the Iraqi forces inspects a tunnel that was used as a training centre by the ISIS jihadists

The base would have been used to train jihadists to carry out atrocities by the terror group

The base would have been used to train jihadists to carry out atrocities.

A commander in the Iraqi army told Rudaw: 'The trainees, as part of their programs, should crawl onto these barrels and get themselves in the mud to pass this phase of training. As you see power has been extended to lighten this base.

'They have fully equipped it without any shortcomings. The majority of those who used to undergo training here were foreigners.'

An Iraqi army commander said most of those trained at the base would have been foreigners

An ISIS flag is seen on the wall in the training base, which was discovered by the Iraqi army in Mosul

Yesterday US-backed Iraqi army units took control of the last major road out of western Mosul that had been in ISIS hands, trapping the militants in a shrinking area within the city, a general and residents said.

The army's 9th Armored Division was within a kilometer of Mosul's Syria Gate, the city's northwestern entrance, a general from the unit told Reuters by telephone.

'We effectively control the road, it is in our sight,' he said.

An Iraqi army general said: 'They have fully equipped it without any shortcomings. The majority of those who used to undergo training here were foreigners'

The base was discovered 10 foot beneath the surface, and had been used to train ISIS fighters to commit atrocities

Mosul residents said they had not been able to travel on the highway that starts at the Syria Gate since Tuesday.

The road links Mosul to Tal Afar, another Islamic State stronghold 40 miles to the west, and then to Syria.

Iraqi forces captured the eastern side of Mosul in January after 100 days of fighting and launched their attack on the districts that lie west of the Tigris river on February 19.

Would-be terrorists could only enter the fortified base by crawling through a tunnel

The US commander in Iraq, Lieutenant General Stephen Townsend, has said he believes US-backed forces will recapture both Mosul and Raqqa, Islamic State's Syria stronghold in neighboring Syria, within six months

If they defeat Islamic State in Mosul, that would crush the Iraq wing of the caliphate declared by the group's leader Abu Bakr al-Baghdadi in 2014 from the city's grand old Nuri Mosque.

The U.S.-led coalition effort against Islamic State is killing the group's fighters more quickly than it can replace them, British Major General Rupert Jones, deputy commander for the Combined Joint Task Force said.

With more than 45,000 killed by coalition air strikes up to August last year, 'their destruction just becomes really a matter of time', he said on Tuesday in London.

The US commander in Iraq, Lieutenant General Stephen Townsend, has said he believes US-backed forces will recapture both Mosul and Raqqa, Islamic State's Syria stronghold in neighboring Syria, within six months.