Phnom Penh - Cambodian human rights group Licadho released 1,700 white balloons outside a prison in the capital Tuesday to draw attention to the plight of two men it said were wrongly convicted of the 2004 murder of a union leader.

The number of balloons represented the total days that Sok Sam Oeun and Born Samnang have served in jail for the January 2004 murder of Chea Vichea, after being sentenced to 20 years in prison in August 2005.

They were convicted despite having apparently watertight alibis. The police officer in charge of their prosecution, Heng Pov, has subsequently been sacked and is now himself in jail on charges including corruption, murder, attempted murder and kidnap.

No date for their Supreme Court appeal - their last legal avenue besides a royal pardon from King Norodom Sihamoni - has been set.

"The two prisoners are in bad condition physically and mentally. We want to draw attention to their imprisonment to make sure this issue is not forgotten and give them strength," Licadho representative Van Sophat said.

Phnom Penh police chief Touch Naroth said the matter was a court issue, but that police had decided not to disrupt a peaceful demonstration and Licadho's budget was its own affair.

"It is up to the organization how they draw attention to the issue and spend their money, but I think if they asked the prisoners, they will ask for food, not balloons," he said.

Cambodian courts are widely accused of lacking independence from the government and are riddled with corruption. (dpa)