BAGHDAD (Reuters) - Iraqi planes dropped millions of leaflets on the western side of Mosul warning residents that the battle to dislodge Islamic State is imminent as troops began moving in their direction, the Defence Ministry said on Saturday.

Slideshow ( 7 images )

The militants are essentially under siege in western Mosul, along with an estimated 650,000 civilians, after U.S.-backed forces surrounding the city forced them from the east in the first phase of an offensive that concluded last month.

The leaflets published on Defence Ministry social media said the troops had begun advancing toward western Mosul.

“Your armed forces (..) are advancing in the direction of the right side, relying on God,” read one of the leaflets, referring to the western side of the northern Iraqi city.

“Get ready to welcome the sons of your armed forces and to cooperate with them, as your brothers on the left side have done, in order to reduce losses and speed up the conclusion” of the battle, added the leaflet.

Other leaflets warned Islamic State members to “lay down their weapons and surrender”, the ministry said in a statement.

The offensive to dislodge Islamic State from Mosul, its last major city stronghold in Iraq, started in October. The hardline Sunni group declared in 2014 a self-styled caliphate that also spans parts of Syria.

The defeat of the group in Mosul would effectively end the Iraqi half of the “caliphate”.

Mosul is the largest city it captured in both countries and its de facto capital in Iraq. Raqqa is its capital in Syria.

Up to 400,000 civilians could be displaced by the offensive as residents of western Mosul suffer food and fuel shortages and markets are closed, United Nations Humanitarian Coordinator for Iraq Lise Grande told Reuters on Saturday. [nL8N1G30CI]

The U.S.-led military coalition said earlier on Saturday its forces had destroyed a building in the main medical complex of western Mosul that was suspected of housing an Islamic State command centre.

The militant group disputed the assertion, saying in an online statement that Friday’s strike had killed 18 people, mostly women and children, and wounded 47 others.

Independent media have no access to western Mosul or other areas under Islamic State control in Iraq and Syria.

The coalition said Islamic State was using the five-storey building as a military command and control facility.

The strike followed reports that the militants are dug in among civilians on the western side of Mosul and storing weapons in hospitals, schools, mosques and churches as a tactic to avoid targeting. [nL8N1G170P]

“The coalition was able to determine through intelligence, surveillance and reconnaissance efforts that ISIS did not use the building for any medical purposes and that civilians were no longer accessing the site,” a coalition statement said, using an acronym for Islamic State.