A new report from the United Nations child relief agency (Unicef) has said that last year saw the highest recorded levels of grave violations against Syria’s children since the outbreak of war in 2011.

At least 652 children were killed in 2016, but since Unicef only records verified deaths, the true figure is likely to be much higher, the agency said on Monday. In addition, at least 850 children were recruited by armed factions to fight.

The number of recorded deaths in 2016 is 20 per cent higher than 2015, and nearly three times as many children were forced to take part in the conflict in 2016 than in the previous year, marking a dramatic increase in the dangers faced by what has been dubbed Syria’s “lost generation”.

Children as young as seven have been forced to fight on the frontline or as suicide bombers and executioners by several rebel groups with links to al-Qaeda, as well as Isis.

During 2016 the Syrian government with the help of Russian warplanes also continued to bomb civilian infrastructure such as schools and hospitals. At least 255 children were killed in or near schools, including a deadly attack in Idlib in October that killed at least 26 people.

At least 850 children were recruited by armed factions to fight (Statista)

The report said both sides showed a “callous disregard” for children’s lives.

The situation for those not caught up in the front lines is still dire: in Syria at least 1.7 million children are out of school, where one in three schools are unusable. There are at least 2.3 million refugee Syrian children elsewhere in the Middle East, with around two thirds of that number forced to work at least part time to support their families.

Save the Children presents Mohammed's story of fleeing the Syrian conflict

“I don’t know how to read or write – I only know how to draw the sky, the sea and the sun,” four-year-old Fares, a Syrian child living in Lebanon, is quoted as saying in the report.

“I’ve waited tables, I’ve served beans, corn, hummus, hookah pipe, potatoes and seeds. I’ve cleaned the shop and and served ice cream to children. I don’t know how to fill the cone but I help [the others] do it. I want to leave my house. It’s like a prison.”

The report also warns that coping mechanisms and medical care are eroding quickly in Syria, driving more children into child labour, early marriage and combat roles. Dozens are also dying from preventable diseases and hunger or stepping on landmines or cluster munitions while playing.

“The situation for Syrian children has hit rock bottom,” Juliette Touma, Unicef’s regional spokesperson, said in a statement.

“The past year has been the worst since the crisis began, with children pushed right to the brink - being recruited at an ever younger age, being used to man checkpoints, being trained to use weapons, serving as prison guards. We also have reports of sexual abuse of girls by underage children, so it’s very grim.”

In pictures: Children play underground in Syria Show all 8 1 /8 In pictures: Children play underground in Syria In pictures: Children play underground in Syria A child plays in the ball pit at the 'Land of Childhood,' an underground playground in a besieged town in Syria Unicef In pictures: Children play underground in Syria Abdulaziz, 10, plays in the 'Land of Childhood' underground playground in Syria Unicef In pictures: Children play underground in Syria Boys look through a show window inside the tunnel that provides a safe passage for children between the two basements that form the 'Land of Childhood' in a besieged town in Syria Unicef In pictures: Children play underground in Syria Children play at the underground 'Land of Childhood' in a besieged town in Syria Unicef In pictures: Children play underground in Syria Two girls play at the 'Land of Childhood' underground playground in a besieged town in Syria Unicef In pictures: Children play underground in Syria Children on the ride on a ferris wheel at the 'Land of Childhood', an underground playground in a besieged town in Syria Unicef In pictures: Children play underground in Syria Seven-year-old Massa at the "Land of Childhood" underground playground in a besieged town in Syria Unicef In pictures: Children play underground in Syria Children wait in line to buy sweets at the 'Land of Childhood,' an underground playground in a besieged town in Syria Unicef

A report released last week by the international charity Save the Children also warned that Syrian youngsters are showing signs of “toxic stress” that can lead to lifelong health problems including struggles with addiction and mental disorders which last into adulthood.

The bloody civil war, which just shy of its sixth birthday shows no signs of slowing down, has killed more than 400,000 people and driven half of Syria’s population from their homes.