A rebel fighter carries his weapon as he moves through a hole in a wall in the old city of Aleppo near the frontline against forces loyal to Syria's President Bashar al-Assad December 28, 2014. (Photo by Jalal Al-Mamo/Reuters)

A mosaic artwork, copied from an original painting, is pictured in a workshop in Kafranbel town in the Idlib governorate January 17, 2015. The mosaic workshop with 30 workers, manufactures artistic and revolutionary mosaics in Kafranbel. Each mosaic artwork takes 5 to 10 days to complete. The artists exhibit their artwork in local and international exhibitions, and have a scheduled exhibition this month about the “Syrian Revolution” in Turkey. (Photo by Khalil Ashawi/Reuters)

A man covered with dust sits on a street following a reported air strike by Syrian government forces in the rebel-held neighbourhood of Sukkari in the northern city of Aleppo on May 30, 2016. (Photo by Baraa Al-Halabi/AFP Photo)

A man reacts over dead bodies prior to burial in a graveyard after shelling in the rebel held besieged town of Douma, eastern Ghouta in Damascus, Syria, October 24, 2016. (Photo by Bassam Khabieh/Reuters)

This Wednesday, August 31, 2016 photo, provided by the Syrian anti-government activist group Aleppo Media Center (AMC), shows Syrian boys dive into a hole filled with water that was caused by a missile attack in the rebel-held neighborhood of Sheikh Saeed in Aleppo province, Syria. (Photo by Aleppo Media Center via AP Photo)

Internally displaced Syrian children who fled Raqqa city stand near their tent in Ras al-Ain province, Syria January 22, 2017. (Photo by Rodi Said/Reuters)

A man carries an injured woman in a site hit by what activists said were airstrikes carried out by the Russian air force in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria January 9, 2016. At least 70 people died in what activists said where four vacuum bombs dropped by the Russian air force in the town of Maaret al-Numan; other air strikes where also carried out in the towns of Saraqib, Khan Sheikhoun and Maar Dabseh, in Idlib. (Photo by Khalil Ashawi/Reuters)

A young Free Syrian Army fighter holds a rifle in Haresta neighbourhood of Damascus January 16, 2013. (Photo by Goran Tomasevic/Reuters)