Libyan forces allied with the U.N.-backed government fire a shell at Islamic State fighters' positions in Sirte, Libya August 15, 2016. (Photo by Ismail Zitouny/Reuters)

Iraqi security forces ride in vehicles travelling to Mosul to fight against militants of Islamic State at an Iraqi army base in Camp Taji in Baghdad, February 21, 2016. (Photo by Ahmed Saad/Reuters)

An Iraqi soldier drives MRAP at his base in Makhmour, after it was freed from control of Islamic State, south of Mosul, April 17, 2016. (Photo by Ahmed Jadallah/Reuters)

A member of Iraqi rapid response forces fires a rocket launcher during a battle with Islamic State militants in the district of Yarimja in southern Mosul, Iraq, January 18, 2017. (Photo by Alaa Al-Marjani/Reuters)

People who fled the violence from Islamic State-controlled northern Syrian town of al-Bab arrive in the rebel-held outskirts of the town, Syria February 3, 2017. (Photo by Khalil Ashawi/Reuters)

An injured man is carried atop an Iraqi special forces armored vehicle during fighting against Islamic State militants in western Mosul, Iraq, Tuesday, March 14, 2017. (Photo by Felipe Dana/AP Photo)

Kurdish pesh merga troops fire at Islamic State positions as they move toward the Iraqi town of Badana Pichwk on Monday morning, October 17, 2016. Kurdish forces began Monday advancing on a string of villages east of Mosul, the start of a long-awaited campaign to reclaim Iraq's second-largest city from the Islamic State, which seized it more than two years ago, officials said. (Photo by Bryan Denton/The New York Times)

Iraqi forces launch a rocket in Mosul's eastern Al-Intisar neighbourhood on December 30, 2016, during an ongoing military operation against Islamic State (IS) group jihadists. Iraqi forces advanced on December 29 after declaring a new phase in their offensive on eastern Mosul, stepping up efforts to reclaim the Islamic State group's last major stronghold in the country. (Photo by Ahmad Al-Rubaye/AFP Photo)