ISIS’s defeat in Mosul three years after taking the city is a major blow for the terrorist group, which is also losing ground in its operational base in the Syrian city of Raqqa from where it has planned global attacks.

The group, however, still controls territory in Iraq and is expected to revert to more conventional insurgent tactics such as bombings as its self-proclaimed caliphate falls apart.

The battle for Mosul – by far the largest city to fall under the militants’ control – has left large areas in ruins, killed thousands of civilians and displaced nearly 1 million people.

“The commander in chief of the armed forces (Prime Minister) Haider al-Abadi arrived in the liberated city of Mosul and congratulated the heroic fighters and Iraqi people for the great victory,” his office said in a statement.

State television later showed Abadi touring Mosul on foot alongside residents of Iraq’s second-largest city.

Airstrikes and exchanges of gunfire could still be heard in the narrow streets of Mosul’s Old City, where ISIS has staged its last stand against Iraqi forces.

Abadi met commanders who led the battle, but he has yet to issue a formal declaration that the entire city has been retaken.

Abadi’s spokesman, Saad al-Hadithi, said victory would not be formally declared until the few remaining ISIS militants were cleared from Mosul.