The Syrian civil war began in 2011, and a new report released by the United Nations' child relief agency, UNICEF, on March 13, says 2016 has been the deadliest year of the conflict for children, with at least 652 killed.

Children have been killed in attacks against schools, playgrounds, parks, and hospitals. 

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.  An additional 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.

The report warns that coping mechanisms and medical care are eroding quickly in Syria, driving children into child labor, early marriage and combat.  Dozens are dying from preventable diseases.

The use of child soldiers is on the rise in Syria, UNICEF said.  At least 851 children were recruited by armed factions last year, more than twice compared to the year before.

Children across the country are at risk of severe injury while playing around landmines and cluster munitions.  Demining operations in opposition-held areas have been severely hampered by inaccessibility to outside experts, according to the report.