Iraqi PM Abadi arrives in Mosul to declare its liberation from IS

The defeat is considererd the biggest yet for the Islamic State group three years since it seized Mosul in a lightning offensive across much of the country's Sunni Arab heartland and proclaimed a "caliphate" straddling Iraq and Syria.

The Iraqi forces launched their campaign to recapture Mosul in October, and since then IS has gone from holding the entire city to being trapped between security forces and the Tigris River on its western side.

Backed by a ferocious aerial bombing campaign by a US-led international coalition, the offensive has turned much of the city to rubble and forced tens of thousands of people to flee.

Diehard jihadists have been putting up fierce resistance in recent days in a tiny area of just two blocks of the Old City next to the Tigris.

Some jihadists were reportedly trying to blend in with fleeing civilians by shaving their beards and changing their clothes, others were playing dead then detonating explosive vests as Iraqi forces closed in.

The battle for Mosul first began on October 17, 2016 and the fight grew tougher when Iraqi forces entered the warren of narrow alleys in the densely populated Old City.

Slowing the advance toward the final holdouts, IS fighters have placed booby traps and bombs in structures they occupied.

A final victory in Mosul marks an epic milestone for the Iraqi security forces, who had crumbled in the face of an IS onslaught across Iraq in 2014.