The United Nations has received reports that Syrian rebels are using child soldiers in their battle against President Bashar al-Assad's forces, a UN official said.
"We are receiving allegations of children with the Free Syrian Army," Radhika Coomaraswamy, UN special representative for children in armed conflict, told reporters.
She however gave no details, saying "we haven't been able to verify or check" the allegations of breaches of conventions banning the use of child soldiers aged under 16.
The Free Syrian Army is led by defectors from Assad's security forces and government, which has refused to let human rights investigators into the country. The UN says well over 8,000 people have died in Syria in the year since an uprising against the president started.
Meanwhile, a leading member of a UN human rights inquiry into Syria quit on Monday, blaming Assad's refusal to let in outside investigators.
Yakin Erturk, a leading international rights expert, left the three-person commission as the UN Human Rights Council extended its mandate for another six months.
"I decided not to continue, mainly because of my concern over not having access to Syria," Erturk told AFP. "This is a serious hindrance of the commission of inquiry."
The commission has produced two reports so far. One released this month said Syrian forces have shot dead unarmed women and children and tortured wounded protesters in hospital under orders from "highest" government officials.
Erturk said she had full confidence that the reports were the best possible, but she felt she had "no more to contribute to the inquiry".
It was important for investigators to keep monitoring Syria, she said, but the UN Human Rights Council would have to decide whether the inquiry commission was the best way.
The council on Friday extended the mandate of the inquiry -- which is led by Sergio Pinheiro of Brazil and also includes Karin Abu Zeid of the United States -- until September when a special investigator could take over.
With the UN Security Council largely deadlocked over how to take action on Syria, the Rights Council's move to set up the inquiry last September was one of the first acts of international pressure on Assad's government.
Erturk is a former UN special human rights rapporteur on violence against women and is still a member of the Council of Europe's committee for the prevention of torture.