The opposition Free Syrian Army forces are reportedly using child soldiers in their battle against the government, the UN said.
The reported allegations were voiced by Radhika Coomaraswamy, the UN special representative for children in armed conflict.
She did not provide any detail, but said the UN has not “been able to verify or check” the accusations so far.
The Free Syrian Army (FSA) is the armed branch of the Syrian opposition waging a guerilla war on against the government. Its leaders claim to have 70,000 people under their command.
The composition of the opposition is hotly debated. Opponents of Syrian President Bashar al-Assad say the FSA is made up of army deserters and their fellow citizens who have taken up arms against the government. Damascus says many of those troops are foreign militants with links to Al-Qaeda.
Last week Human Rights Watch said the FSA and other oppositional forces were engaged in kidnappings, torture and unlawful executions of prisoners.
Syria has been embroiled in turmoil since February 2011, when mass protests against the government swept across the country. The conflict soon turned violent, as security forces and armed opposition members clashed.
The opposition says it is fighting for their freedom against an oppressive regime. The government says it is quashing a foreign-sponsored incursion of terrorists who hijacked the popular protest.