A member of the Iraqi Federal Police looks on as they clash with the Islamic State fighters in western Mosul, Iraq, April 24, 2017. REUTERS/Muhammad Hamed

Federal police members prepare their munitions during a battle with Islamic State fighters at Bab al Beed district in the old city of Mosul, Iraq, March 31, 2017.

Civilian family waves a white flag during a battle with Islamic State militants in Mosul, Iraq April 4, 2017 .

A soldier of Iraqi army sits in a tank during clashes between Iraqi forces and Islamic State militants, in Mosul, Iraq March 25, 2017.

Federal police members aim their weapons at a man, whom they thought was a member of Islamic State but later turned out to be mentally handicapped, during a battle with Islamic State fighters at Bab al Beed district in the old city of Mosul, Iraq, March 31, 2017.

Iraqi rapid response members fire a missile against Islamic State militants during a battle with the militants in Mosul, Iraq March 29, 2017.

Members of the Iraqi Federal Police take a break from fighting the Islamic State in western Mosul, Iraq, April 24, 2017.

Iraqi Federal Police members push a trolley loaded with munitions in a street controlled by Iraqi forces during a break in combats against Islamic State in Mosul, Iraq April 3, 2017. REUTERS/Andres Martinez Casares - RTX33UDM

Members of the Iraqi Federal Police clash with the Islamic State fighters in western Mosul, Iraq, April 24, 2017.

An Iraqi Air Force helicopter fires a missile against Islamic State militants during a battle in Mosul, Iraq March 28, 2017.

A toy skeleton is seen on a military vehicle of the Iraqi Counter Terrorism Service forces after their battle with Islamic State militants in western Mosul, Iraq, April 22, 2017.

A member of Iraqi Federal Police takes his position during a battle against Islamic State militants at Bab al Jadid district in the old city of Mosul, Iraq, March 27, 2017.

Federal police members drive a military vehicle during a battle at Jada district in Western Mosul, Iraq March 29, 2017.

A stuffed animal lies on a couch next to a rifle in a house used by Iraqi Federal Police as a position to fight the Islamic State in Mosul, Iraq, April 4, 2017.

Iraqi children carry water containers after the battle between the Iraqi Counter Terrorism Service and Islamic State militants in western Mosul, Iraq, April 22, 2017. Image for illustrative purpose.

Federal police members detain a man, whom they thought was a member of Islamic State but later turned out to be mentally handicapped, during a battle with Islamic State fighters at Bab al Beed district in the old city of Mosul, Iraq, March 31, 2017.

Iraqi Federal Police members clash with Islamic State militants during a battle in Mosul, Iraq April 4, 2017 .