Smoke billows following a reported air strike on a rebel-held area in the southern Syrian city of Daraa, on April 16, 2017. / AFP PHOTO / Mohamad ABAZEED (Photo credit should read MOHAMAD ABAZEED/AFP/Getty Images)

Smoke billows following a reported air strike on a rebel-held area in the southern Syrian city of Daraa, on April 16, 2017. / AFP PHOTO / Mohamad ABAZEED        (Photo credit should read MOHAMAD ABAZEED/AFP/Getty Images)