A rescue worker holds an injured boy after what activists said were airstrikes carried out by the Russian air force in Idlib city, Syria December 20, 2015. (Photo by Ammar Abdullah/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)