Rebels fighting for the Free Syrian Army are using children as fighters, a U.N. official charges.
Syrian rebels fighting against the Bashar al-Assad regime's security forces have been accused of recruiting and using child soldiers, which violates international conventions.
"We are receiving allegations of children with the Free Syrian Army," Radhika Coomaraswamy, U.N. special representative for children and armed conflict, said without giving further details.
"We haven't been able to verify or check" the veracity of those allegations, Coomaraswamy added.
The accusations followed a report by Human Rights Watch that rebels were engaged in abuses including "kidnapping, detention, and torture of security force members, government supporters, and people identified as members of pro-government militias, called shabiha."
HRW added that it had also received reports of "executions by armed opposition groups of security force members and civilians."
Although the watchdog pointed out that most of the human rights violations had until now been attributed to Assad's regime, the new accusations will come as a blow to Syrian opposition groups.
In the last few weeks the Syrian army has regained control of most of the FSA strongholds, and despite defections Assad's army remains strong.
In contrast the opposition has been criticised for being divided.
In February, tensions were exposed after prominent members of the Syrian National Council, the main umbrella opposition group, withdrew from the coalition.
Members complained that the country's Muslim Brotherhood, which draws support from the Sunni majority, had too much influence over the SNC's leadership.
The group retaliated by unveiling a new political charter that called for the establishment of a democratically elected government.
In an attempt to unify the opposition groups, a series of meetings are taking place in Istanbul ahead of an Arab League meeting on 1 April.
UN Right Experts Quits Inquiry into Syria
A leading member of a UN human rights inquiry into Syria has quit.
Yakin Erturk, a leading international rights expert, said she had resigned because of Assad's refusal to let outside investigators enter the country.
"This is a serious hindrance of the commission of inquiry," she told AFP.
The U.N. Human Rights Council set up a three-person commission in September to probe alleged abuses in Syria.
The commission presented its latest report to the council earlier in March and documented "patterns of summary execution, arbitrary arrest, enforced disappearance, torture, including sexual violence, as well as violations of children's rights by Syrian security forces."