The deaths have been caused by all sides in the conflict. A report by UN Secretary-General Ban Ki-moon blamed "indiscriminate and disproportionate aerial bombings and ground attacks" on areas with large civilian populations by government forces, opposition fighters and "terrorist" groups. Geoffrey Mock, a Middle East specialist at Amnesty International, said both government forces and insurgents have used "weapons that are guaranteed to cause civilian damage".
"What we are seeing in Syria is war crime on both sides," Mock told the
New York Times.
The conflict in Syria is now approaching its fifth year with no end in sight. Of the four million people who have fled the country, nearly two million of them are children. Almost three million children are unable to go to school (2.3 million inside Syria, 685,000 refugees).
IBTimesUK looks at the lives – and tragic deaths – of children in Syria.
A man holds an injured child after a Syrian army fighter jet crashed into a busy market place in Ariha on 3 August 2015
A civil defence member carries an injured baby who was pulled out from under debris at a site hit by what activists said was an airstrike by forces loyal to Syria\'s President Bashar al-Assad in the town of Marshamsha, Idlib province, on 20 October 2015
Ghazal, 4, and Judy, 7, carrying 8-month-old Suhair, react after what activists said was shelling by forces loyal to Syria\'s President Bashar al-Assad near the Syrian Arab Red Crescent centre in Douma on 6 May 2015
A man holds a baby who survived what activists said was a barrel bomb dropped by Assad\'s forces on the old city of Aleppo, on 3 June 2015
A girl is evacuated from a site hit by what activists said were air strikes by forces loyal to Syria\'s President Bashar al-Assad in the Douma neighbourhood of Damascus on 24 August 2015
A child sits in a pushchair filled with cartons collected to use for heating in Douma, on 17 November 2015
A boy rides a tricycle along a damaged street in Homs, on 1 January 2014
Students attend a class inside the bombed and partially destroyed Hosam Kamel school in the rebel-controlled area of Maaret al-Numan town in Idlib province, on 28 October 2015
A boy looks at the camera in a school near Idlib, on 20 September 2015
Children attend a class in a school in the countryside around Idlib on 20 September 2015. The text near the drawing of the tank reads: \"Whoever kills his people is a traitor\"
Girls write in a classroom at a primary school in Aleppo on 4 October 2015
Children look out from a window at a school in a rebel-controlled area of the eastern Ghouta, Damascus, on 19 October 2015
A vendor sells bags ahead of the start of the school year in the old al-Qanawat neighbourhood of Damascus, on 12 September 2015
A girl raises her hand during class at a school in Qamishli, in the predominantly Kurdish Rojava region of northern Syria, on 12 November 2015
John Moore/Getty Images
Children play with toy weapons along a street in the al-Jazmati neighbourhood of Aleppo on 1 February 2015
Boys play with a pipe, pretending it is a mortar, at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria\'s President Bashar al-Assad in the old city of Aleppo on 12 July 2015
A boy plays with a toy gun in the Syrian Mediterranean port city of Latakia on 24 September 2015, the first day of Eid al-Adha
Children wearing face masks play table football during a sandstorm in Homs, on 7 September 2015
A boy walks past damage after a Syrian army fighter jet crashed into a busy market place in the rebel-held northwestern town of Ariha on 3 August 2015
A girl stands on a damaged building after what activists said were air strikes by forces loyal to Syria\'s President Bashar al-Assad in the Douma neighbourhood of Damascus on 6 February 2015
A boy sweeps debris off a road at a site damaged by what activists said was a barrel bomb dropped by Assad\'s forces in the historic Syrian town of Bosra al-Sham, Deraa province, on 21 October 2015
A boy flashes a victory sign near stalls where fish and chicks are displayed for sale during the festival of Eid-al-Adha in Idlib, on 24 September 2015
A boy dives into a crater filled with water in Aleppo\'s al-Shaar district on 10 July 2014. Activists said the crater was caused by barrel bombs dropped by forces of Syria\'s President Bashar al-Assad
A child sifts through rubbish at a landfill in the rebel-held part of the northern city of Aleppo, on 27 October 2015
Boys receive treatment at a makeshift hospital following reported air strikes by government forces in Douma, on 29 October 2015
A wounded Syrian boy cries at a makeshift hospital following a reported air strike by government forces in the rebel-held area of Douma, on 18 November 2015
Children who have lost one or both of their parents in Syria\'s ongoing conflict line up to attend a party organised for them by the local NGO Douma Society in the rebel-held district of Douma, east of Damascus, on 28 September 2015
A wounded girl stands in a makeshift hospital in the rebel-held area of Douma following shelling and air raids by Syrian government forces on 22 August 2015
A Syrian man carries the body of a child killed in a reported air strike by government forces in the rebel-held area of Douma, on 7 November 2015
A man holds the body of his daughter who was killed by what activists said were air strikes by forces loyal to Syria\'s President Bashar al-Assad in the Douma neighbourhood of Damascus, on 24 August 2015
A Syrian man carries the body of a child following a reported military strike by government forces in the rebel-controlled Bustan al-Qasr district of the northern city of Aleppo on 20 June 2015
Save the Children is working inside Syria to give children the basics they need to survive. The organisation is providing urgent relief as well as long-term aid to refugee children in neighbouring countries, such as Lebanon and Iraq, and along the route through Europe. You can help.