Sri Lanka's Tamil Tiger rebels have been recruiting child soldiers from relief camps set up after December's tsunami, the United Nations says.
The Tigers have routinely denied they are still recruiting underage fighters
The UN's child agency, Unicef, says it has monitored the cases of three girls who had been recruited by the rebels.
"In the aftermath of the tsunami, you would have hoped that recruitment would have stopped," Unicef's Victor Nylund told the BBC News website.
The Tamil Tigers have denied any involvement in the incidents.
The rebels and the government are in a bitter dispute over aid provision.
The issue of child recruitment has been a major point of difference between Unicef and the Tamil Tigers since a ceasefire began in early 2002.
Correspondents say the issue is particularly sensitive now, given the arguments between the rebels and the government about the distribution of aid in areas of Sri Lanka controlled by the Tigers.
'All efforts needed'
"We have enough proof that these children had gone missing from the camps and are now with the LTTE [Tamil Tigers], " the head of Unicef in Sri Lanka, Ted Chaiban, told reporters on Thursday.
A senior LTTE leader told the BBC's Tamil Service that the rebels had not been involved in the incident. He questioned Unicef's decision to talk to the media without first discussing the issue with the rebels.
The Tamil Tigers repeatedly denied reports last year that they were recruiting underage fighters.
Unicef says one child, a girl, was recruited in Batticaloa. Two other girls, from the same family, were recruited from a camp in Amparai, Unicef says.
The UN agency said later on Thursday that the girls in Amparai had now been reunited with their family.
Unicef's Victor Nylund said that having to monitor child recruitment was taking away resources that Unicef could be better using to help children affected by the tsunami.
"All efforts are needed in the relief effort, especially for orphaned and separated children," he said.
Unicef estimates the Tamil Tigers have some 1,300 child soldiers.
Peace talks with the government stalled in 2003.
The main stumbling block is the Tigers' demand for an interim autonomous administration in the north and east of the country.