At least 652 children died in the last 12 months, a 20% increase on 2015, the organization said in a damning new report
Nearly half of those children were killed in or near school
The report includes only verified figures, meaning the death toll could be much higher, the report said.
"I wanted to become a doctor but perhaps I won't become anything because our school was attacked," 6-year-old Ahmad is quoted as saying.
"We used to play a lot in the schoolyard but now I'm afraid of coming here."
At least 850 children were recruited to fight in the conflict in 2016 -- more than double the number the year before, the report said. Increasingly, children were being used to fight on the frontlines and in combat roles, "including in extreme cases as executioners, suicide bombers or prison guards."
"Each and every child is scarred for life with horrific consequences on their health, well-being and future," Geert Cappelaere, the UNICEF Regional Director for the Middle East and North Africa speaking from Homs, Syria, said in a statement.
Nearly six million children now depend on humanitarian assistance, says UNICEF
, 12 times the number in 2012.
Additionally, UNICEF says it can't even access some of the harder to reach parts of the country, where it estimates 280,000 children are living under siege "completely cut off from humanitarian aid" and "dying in silence often from diseases that can otherwise be easily prevented."
Last week, British charity Save the Children published a report
which stressed that Syria's children were suffering from "toxic stress" brought on by the sheer brutality of the ongoing civil war.
At least three million Syrians under the age of six "know nothing but war," said Save the Children, adding that prolonged exposure could lead to a number of problems, including self-harm and suicide attempts.
In the report, one father named Firas recounted how his 3-year-old, Saeed, had been affected.
"My son wakes up afraid in the middle of the night," he said.
"A child was slaughtered in front of him, so he started to dream that someone is coming to slaughter him. When a child witnesses a beheading, how could he not get afraid?"
Since the war began in 2011, an estimated 400,000 Syrians have been killed in what the United Nations
is calling the worst humanitarian crisis since World War II.