Children as young as 11 are being snatched off the streets of Burma, given military training and then coerced into battle, a new report from the Human Rights Watch group says.

Most of the boys end up in the national army where 70,000 soldiers are estimated to be under the age of 18, though armed opposition groups use them as well, according to the report.

Jo Becker of Human Rights Watch said: "To be a boy in Myanmar today means facing the constant risk of being picked up off the street, forced to commit atrocities against villagers, and never seeing family again."

The New York-based advocacy group published its 220-page report - My Gun was as Tall as Me - and said it was the most comprehensive study of its kind.

Burma - which is also known as Myanmar - often comes under attack for its record on human rights, in particular its treatment of ethnic minorities and pro-democracy campaigners including Nobel peace laureate Aung San Suu Kyi.

The international community has moved against using children as fighters and a UN ban is now in force.

Official denials

The military government denied the allegations in the new report.

"The government finds it very difficult to understand on what basis it is making such claims, saying that 20% of the national army is made up of underage children," it said in a statement.

Human Rights Watch said its researchers held extensive interviews with current and former child soldiers and examined recruitment by the national army and 19 different armed opposition groups to compile the report.

Its findings said:

• Army recruiters apprehend boys at train and bus stations and markets, threatening them will jail if they object

• The boys are given no chance to contact their families

• They are sent to camps for weapons training

• Beatings are common and punishments severe if the boys try to escape

• Then they are sent into combat

Salaing Toe Aung, recruited when he was 16, is quoted in the report as recalling a recaptured escapee who was beaten about the head and back with sticks for 30 minutes before being placed, unconscious, in leg stocks for a week.

"He couldn't eat anything and they sent him to the hospital. He died in the hospital," he said.

Witness to atrocities

Khin Maunh Than was 13 when his army unit captured 15 women and children, including three babies.

The adults were shot and the babies beaten to death on rocks, he said.

Burma's most renowned child fighters - twins Luther and Johnny Htoo - sought refuge in Thailand early last year after leading a rebel band of fighters from the Karen ethnic minority known as God's Army.

They cried when they were reunited with their mother and rejected the claims of some of their followers that they had mystical powers protecting them from bullets and land mines.