Debris fly as smoke rises after an artillery attack on ISIS militant positions by the Iraqi Army in the Shifa neighbourhood during clashes in western Mosul, Iraq June 15, 2017.

:: Iraqi forces began storming the ISIS-held Old City of Mosul on Sunday, an assault they hope will be the last in the eight-month campaign to seize the militants’ stronghold.

The historic district is the last still under control of the militants in the city, which used to be the Iraqi capital of the group, also known as ISIS.

“Iraqi forces early this morning breach into old Mosul, the final ISIS-held district in the city,” Brett McGurk, the US envoy to the international coalition fighting ISIS, said on Twitter. “We are proud to stand with them.”

It is a densely-populated maze of narrow alleyways where fighting is often conducted house by house.

About 100,000 civilians remain trapped there in harrowing conditions, with little food, water and medicine and limited access to hospitals, according to the United Nations.