A combination picture shows Aleppo's Umayyad mosque, Syria, before it was damaged on March 12, 2009 (top) and after it was damaged (bottom) December 13, 2016. (Photo by Omar Sanadiki/Reuters)

A Syrian boy looks through a gate as others wait to cross into Syria at Oncupinar border crossing in the southeastern city of Kilis, Turkey February 11, 2016.. (Photo by Osman Orsal/Reuters)

A girl pours water over a dog to cool it down, in the rebel held besieged town of Douma, eastern Damascus suburb of Ghouta, Syria, June 23, 2016. (Photo by Bassam Khabieh/Reuters)

Iraqi government forces are seen near the Falahat village west of Fallujah on June 27, 2016. Iraqi forces took the Islamic State group's last positions in the city of Fallujah on June 26, establishing full control over one of the jihadists' most emblematic bastions after a month-long operation. (Photo by Moadh Al-Dulaimi/AFP Photo)

An injured Iraqi Emergency Response Division (ERD) soldier hit by a mortar is held by another officer as they wait for medics to arrive at the Islamic State occupied Mosul Airport in west Mosul, part of the offensive to retake the city some two years after it fell to the hardline jihadist group, February 23, 2017. Iraqi forces encountered stiff resistance with improvised explosives, heavy mortar fire and snipers hampering their advance before they successfully took the airport. (Photo by Martyn Aim/Getty Images)

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)

A Swiss police officer accompanies a migrant from Syria carrying her baby, upon her arrival at the railway station in the north-eastern Swiss town of Buchs September 1, 2015. (Photo by Arnd Wiegmann/Reuters)

Internally displaced Syrian children stand at the entrance of their makeshift shelter that is an underground cave in Om al-Seer, southern Idlib countryside, Syria December 26, 2015. (Photo by Khalil Ashawi/Reuters)