Tamil children 'being abducted'
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).
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.