BEIRUT — At least 652 children were killed in Syria in 2016, making it the worst year yet for the country’s rising generation, the United Nations’ child relief agency said Monday.

There was no letup to attacks on schools, hospitals, playgrounds, parks and homes last year as the Syrian government, its opponents and the allies of both sides showed callous disregard for the laws of war.

UNICEF said at least 255 children were killed in or near schools last year and 1.7 million youngsters are out of school. One of every three schools in Syria is unusable, some because armed groups occupy them. Another 2.3 million Syrian children are refugees elsewhere in the Middle East.

The figures come in a UNICEF report released two days before the sixth anniversary of the popular uprising that escalated into civil war.

Children were among the first victims of the government’s brutal crackdown. On March 15, 2011, residents in the southern city of Daraa marched to demand the release of teenage students who were tortured in detention.