Syria's children "hit rock bottom" in 2016, with more killed than in any other year of the civil war, Unicef has said.
At least 652 children died - 255 of them in or near a school - last year, a 20% jump from the number killed during 2015, the organisation said.
The figure only includes the deaths formally verified, meaning the number could be far higher.
Unicef also believes more than 850 children were recruited to fight.
The number is double that of 2015, the report states. Those recruited increasingly found themselves on the frontline, or in extreme cases used as executioners, suicide bombers or prison guards.
"The depth of suffering is unprecedented," said Geert Cappelaere, Unicef regional director for the Middle East and North Africa speaking from Homs, Syria.
"Millions of children in Syria come under attack on a daily basis, their lives turned upside down."Image copyright Reuters Image caption Some six million children are relying on humanitarian aid after six years of war
Six million children are now relying on humanitarian aid due to the civil war, which has been raging for six years this week.
Some 2.3 million have fled the country, but the most vulnerable are the 2.8 million trapped in hard to reach areas, which includes 280,000 living under siege, Unicef said.
Mr Geert added: "Each and every child is scarred for life with horrific consequences on their health, well-being, and future."
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Last week, Save the Children warned millions of Syrian children could be living in a state of "toxic stress", which the charity feared may become irreversible without immediate help.
It also found two-thirds of children had either lost a loved one, had their house bombed or shelled, or been injured as a result of the war.