The UN childrens fund, UNICEF, called on the Sri Lankan government to halt the abduction of child soldiers by a Tamil rebel group led by V Muralitharan - also known as Colonel Karuna.
"Over the past week, the agency has verified reports of 30 cases in (the eastern) Batticaloa district," UNICEF said in a statement.
"Reports of abduction and forced recruitment of boys under the age of 18 have increased since March," it added.
"These gross violations of their rights will also expose children to brutality and extreme violence with lifelong consequences," the statement said.
The main Tamil Tiger rebel group released 33 children last month, saying that they had lied about thier ages to join the organisation.
New York-based Human Rights Watch, in a November 2004 report, said UNICEF had documented 3,516 new cases of underage recruitment by the Tamil Tigers between February 2002, when a ceasefire was reached with the government, and October 2004.
Poverty, abuses by Sri Lankan security forces, rebel propaganda and coercion often fuel the recruitment of children, the rights watchdog said.