By Frances Harrison BBC correspondent in Colombo

The girl on the right has recently been released by the Tigers

Unicef say their investigations have revealed that the releases took place after recent factional fighting in the east of the island.

But a statement from the US-based Human Rights Watch group expressed concern that they may be recruited again.

Unicef say only about a quarter of those released were on their database.

'Many new cases'

Unicef says about 200 child soldiers were formally released by the mainstream faction of the Tamil Tigers when they quashed a rebellion in the east of the country by a breakaway commander two weeks ago.

Another 1,100 children were sent home or allowed to ran away.

The rebels are accused of encouraging former fighters to re-enlist.

Unicef says it has investigated these cases and ascertained they are all child soldiers.

What is most worrying is that only about a quarter of the released child soldiers were on their database.

This comprises a list of more than 1,000 cases based on reports of abductions and complaints from parents.

Because so many new cases are coming to light now, the assumption is that child recruitment was much more extensive than previously thought.

Indeed human rights activists have long maintained that only about a quarter of the child recruitment cases were ever reported.

And a statement from the New York based Human Rights Watch organisation says it has reports that the rebels are making announcements on loudspeakers on vans in the east encouraging former fighters to re-enlist.

Unicef says it cannot confirm this, but local people in the east say there are rumours that the disbanded child soldiers are returning to the rebel movement for want of other options.