At least 10,000 civilians were killed in the final months of Sri Lanka's civil war but a national inquiry has failed so far to investigate war crimes committed by both the army and Tamil rebels, Amnesty International charged on Wednesday.
The London-based human rights group called on the United Nations to establish a credible international investigation into the deaths in 2009, the year that ended the quarter-century conflict.
Although the national commission set up by President Mahinda Rajapaksa in May 2010 has heard evidence of serious violations - including what Amnesty called proof of the army shelling civilian areas and the use of human shields by the Liberation Tigers of Tamil Eelam (LTTE) - the official inquiry has failed to recommend any prosecutions, it said.
The Lessons Learnt and Reconciliation Commission is due to present its report to the Colombo government in mid-November. Amnesty and other groups rejected an invitation to present evidence to it, saying the inquiry would not be credible.
"Amnesty International urges the international community not to be deceived that the Lessons Learnt and Reconciliation Commission - the latest in a long line of failed domestic mechanisms in Sri Lanka - will deliver justice, truth and reparations to the tens of thousands of victims of war crimes, crimes against humanity and other crimes committed during the conflict by both sides, particularly during its last bloody few months," the report, running to almost 70 pages, said.
Amnesty accused government forces of large-scale shelling of no-fire-zones where it had encouraged the civilian population in the northeast to concentrate.
"Most civilian casualties in the final phases of the war were caused by government shelling."
The report was based on eyewitness testimony, information from aid workers deployed at the time and transcripts of hearings held by the national inquiry.
The government silenced the media and other critics of the war and rounded up opponents, some through "the use of white vans to abduct and to make people disappear", Amnesty said.
There was no immediate comment from the government on the report, made available to reporters ahead of its release.
Sri Lanka's Foreign Minister G.L. Peiris is on a mission to shore up diplomatic support ahead of a three-week session of the U.N. Human Rights Council opening on Monday where the Indian Ocean nation expects to face a fight over Western-led pressure for a war crimes probe.
The government rejects the death tolls as vastly inflated by pro-Tiger groups and mathematically impossible given the number of refugees accounted for after the war against even the highest reported tally of civilians in the conflict zone at the war's end. It says it was difficult to distinguish between civilians and combatants, given Tiger fighters routinely blended into the population.
Sri Lanka is now in its third year of peace after destroying the Tamil Tiger separatists, listed by more than 30 nations as a terrorist organisation.
Sri Lanka has said it was impossible to avoid all civilian casualties during the final offensive to wipe out the Tigers, who held nearly 300,000 people as human shields, but says its troops used only necessary and lawful force.
A UN panel of international experts, in a report submitted last April to UN Secretary-General Ban Ki-moon, found "credible evidence" that Sri Lankan forces and the LTTE committed war crimes and killed thousands of civilians in the war's last months in 2009.
Colombo has managed to stave off censure at UN forums thanks to the support of close allies China and Russia, but a vote at the Human Rights Council cannot be blocked by veto-wielding powers.
"History demonstrates that Sri Lanka lacks the political will to address serious allegations of abuse or to end impunity," the Amnesty report said.
"It (the government) has not attempted to identify government personnel alleged to be responsible for violations of international human rights and humanitarian law committed in the final stages of the armed conflict, let alone initiate steps necessary to ensure that justice is served," it added.
Aid workers in the war zone at the end of the conflict were almost entirely Sri Lankan Tamils, after the government told foreign aid workers it could not guarantee their safety and they withdrew.
The majority of complaints fell into three broad categories: missing persons, including forced disappearances, detentions, and economic hardship as a result of the armed conflict and people being forced to flee their homes, Amnesty said.
"Unfortunately Commissioners failed to ask follow-up questions of witnesses that would have allowed them to lay a foundation for a criminal inquiry," it said.
"A few witnesses named individual perpetrators, though the Commissioners did not pursue these claims," it said, calling the commission "flawed at every level".
The national inquiry is headed by C.R. de Silva, a former attorney general. Its members include former government officials who have publicly defended Sri Lanka against charges of war crimes, including at the UN, according to Amnesty.
Sri Lanka has also accused the UN panel of bias. Its head, former Indonesian attorney general Marzuki Darusman, was publicly critical of the government prior to his appointment.