BANGKOK - A TOP leader of Myanmar's rebel Karen National Union who was also a key figure in the democracy movement was assassinated on Thursday at his home in Thailand, Thai police and political exiles said.

Pado Manh Sha, 65, was KNU's secretary general based in the Thai town of Mae Sot. Mae Sot police commander Colonel Passawat Teangjui said he was killed on Thursday afternoon at his home by three gunmen who spoke the Karen language.

'His relatives who witnessed the killing said the first man went up to greet Pado Manh Sha while he was resting, but then shot him once. A second man came up and shot him again,' Mr Passawat said.

Mr Win Min, a Thailand-based Myanmar analyst, said the death of KNU's third-highest leader was a major loss for the Karen.

'He is one of the top leaders for the group. He is an articulate strategist and a unifying figure for the KNU,' Mr Win Min said.

Myanmar exiles said Pado Manh Sha could have been killed by a Karen splinter group or by assassins ordered by the military, which has ruled the country formerly known as Burma since 1962.

'It is likely to be a KNU problem,' said Myanmar analyst Aung Naing Oo, noting that the mainly Christian KNU sometimes battles with a Buddhist splinter group called the Democratic Karen Buddhist Army (DKBA).

But he said that dissidents along the border were scared that the killing was ordered by the junta, which might want to target other exile leaders.

'Everybody is terrified that there could be a hit list from the Burmese military circulating around Thailand of people to be killed,' he said.

'So far nobody knows who did it,' he added.

'This is very damaging. He is very well known, very committed, and he is also on the side of the pro-democracy movement. The repercussions will affect more than just the KNU,' Mr Aung Naing Oo said.

The KNU has battled Myanmar's rulers for nearly six decades in one of the world's longest-running insurgencies.

The KNU is the largest rebel group fighting Myanmar's armed forces and one of the few remaining ethnic insurgencies yet to sign a peace deal with the junta.

The group once controlled broad swaths of eastern Myanmar but now is reduced mainly to a string of bases pressed against the Thai border.

Myanmar began a bloody offensive against the Karen two years ago, which activists say has targeted ordinary villagers rather than rebels.

Decades of fighting have devastated eastern Myanmar, where 500,000 people have been displaced by violence, according to Human Rights Watch.

Up to 150,000 Karen refugees also live in camps along Thailand's border with Myanmar. Many of them have been there for more than 20 years.

Rape, forced labour, summary executions and land grabs remain widespread, while the military also forced villagers to act as human minesweepers, Human Rights Watch said in its annual report last month. -- AFP