Sue Lloyd Roberts in Sri Lanka meets the children fighting an adult's war

Unicef estimates there are around 500,000 children fighting in various wars throughout the world, particularly Sri Lanka, Afghanistan and Uganda.

In Sri Lanka, the Tamil Tigers, who are fighting for a separate homeland, have been employing children in their guerrilla forces for seven years.

The Tamil Tigers say the government is driving children to them

The BBC correspondent in Sri Lanka says that, in some areas held by the Tamil Tigers, up to 50% of pupils have left schools to join the Liberation Tigers of Tamil Eelam (LTTE).

One young Tamil recruit said she knew how to lay landmines and operate machine guns and pistols by the age of 13.

"The leaders came to our school and said we had to join the army in order to rescue our country," she said.

"After three months I was sent to my first operation. It was an attack on an army checkpoint and I was equipped with grenades."

The risk of being killed or injured is not the only threat to the lives of the Tamil child bombers.

Suicide capsules

All new recruits are given cyanide capsules with instructions to swallow them if captured to avoid giving military secrets to their enemies.

This girl was trained to kill at 13

Sri Lanka's foreign affairs minister Lakshman Kadirgama said: " It reminds me very much of what happened to the German youth under Hitler towards the end of the of the Second World War. Hitler was recruiting teenagers, as young as 13 and 14."

But a recruitment officer for the Tamil Tigers insisted that no pressure was being put upon youngsters to join the LTTE.

"It is not the Tigers who are recruiting young people, it is the government who are driving the children to the Tigers," he said.

"A young person loses a parent - they feel real anger and they vent this anger by joining the Tigers."