More than 250,000 people have been killed and 11 million forced to flee their homes in almost five years of fighting in Syria. Thousands of internally displaced people are now massed on the border with Turkey. But right now only ambulances and a limited number of refugees are allowed to cross.

Around 50 people were killed in February when a series of airstrikes hit schools and hospitals in two rebel-held towns in northern Syria. The Turkish government blamed one set of strikes on Russia, while UN Secretary-General Ban Ki-moon slammed the attacks as "blatant violations of international laws."