A UN envoy has warned that Syria's devastating conflict, now in its third year, will force a generation of children to grow up illiterate and filled with hate.

Leila Zerrougui, the special representative for children and armed conflict, says both sides of the Syrian conflict continue to commit grave violations against children.

She says scores of children have been killed, injured, detained, and forced to witness or to commit atrocities as President Bashar Al-Assad's troops battle opposition fighters trying to oust his regime.

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Zerrougui also said on Thursday that thousands of schools have been destroyed.

"Children who are desperate and full of anger would like to seek revenge. And they will not have access to schools, which mean that a future generation – if this conflict continues – will be illiterate and exposed to radicalisation,” Zerrougui told Al Jazeera.

She spoke after a visit to Syria where she met government officials and rebel commanders.

She urged both sides to spare the children.

Thousands of children have died since the war began in 2011, according to the UN. It said there have been cases where children have been tortured and executed.

A UN report, released in June, said both government forces and rebels have been using boys and girls as suicide bombers or human shields.

Source: Al Jazeera and agencies