Fighting displaced at least a quarter of a million Tamils, the UN says
A number of children in camps for people displaced by Sri Lanka's conflict have been abducted, international human rights groups say.
The groups say they have verified reports of disappearances in the Vavuniya area and are calling for the United Nations to investigate.
Suspected former Tamil Tiger child soldiers are said to have been removed by paramilitaries for questioning.
A Sri Lankan military spokesman denied the groups' allegations.
A spokeswoman for the groups, Charu Lata Hogg, said the motives for the abductions were unclear but some children were being questioned about alleged links to the Tamil Tiger rebels, or LTTE (Liberation Tigers of Tamil Eelam).
Tens of thousands of children were among those displaced in the recent fighting, many finding themselves in government-run refugee camps.
On Tuesday, Sri Lankan President Mahinda Rajapaksa declared the country "liberated" from Tamil Tiger rebels after a 26-year war.
He spoke after the army reported the death of rebel leader Velupillai Prabhakaran and the capture of the last pocket of territory held by the Tigers.
'Kidnapped for ransom'
The Coalition to Stop the Use of Child Soldiers is an umbrella group of global organisations which includes Amnesty International and Human Rights Watch.
It said it had received verified reports of abductions from camps in and around Vavuniya in the north.
It alleges that groups like the EPDP, PLOTE and the TMVP-Karuna faction - all Tamil paramilitary groups affiliated to the government - have unfettered access to the camps despite the presence of the Sri Lankan military.
"The motive is slightly unclear," said Ms Hogg.
"Some are being taken away for ransom, they've been kidnapped for ransom, and there've been certain negotiated releases where mothers had some jewellery and they could negotiate a release right within the camp.
"In other cases the children have been taken away for questioning for their alleged links to the LTTE, so they are suspected of being former child soldiers with the LTTE."
She says there are fears for the safety of former LTTE child soldiers, who should be protected under international agreements.
Sri Lanka's military denied the allegations, describing them as yet another attempt to discredit the government.
Military spokesman Udaya Nanayakkara said it was impossible for "anyone, even a child or an LTTE person, to be taken out from the camps without any proper or legal authority".
The coalition says the protection of children in the north and east of Sri Lanka is a matter of urgent concern, citing the refusal of access to international agencies responsible for monitoring the camps.
Without independent scrutiny, it says, children are at risk of human rights abuses, arbitrary detention and enforced disappearance.