The UN study says that since 1980, 12,000 Sri Lankans have gone missing after being detained by security forces.

More than 55,000 people have been killed over the issue in the past 27 years.

Only Iraq had more cases of disappearances, with 16,384 missing, according to the study by the United Nations Working Group on Enforced or Involuntary Disappearances.

But the figures are still lower than the current Sri Lankan government's own estimate of 17,000 people missing, which was made after it came to power with a commitment to correct the human rights.

Investigation planned

According to the UK's Sunday Times newspaper, a UN working group investigating the disappearances will soon be allowed to visit Sri Lanka.

Last week, the Sri Lankan cabinet approved a method for conducting the investigations and appointed a committee to administrate the investigation.

President Kumaratunga's People's Alliance Party came to power in 1994 promising to correct the human rights abuses of the previous decade.

But her critics says she is doing little to address the root causes of the disappearance problem.