Bishop Rayappu Joseph of Mannar and Bishop Thomas Savundaranayagam Emmanuel of Jaffna reiterated the demand during a meeting with Stephen J. Rapp, U.S. ambassador-at-large for war crimes issues in the State Department's Office of Global Criminal Justice, in early January in Jaffna.

"We want to know what happened in the last few days of the war," Bishop Emmanuel, who hosted the meeting, later told Catholic News Service.

On Jan. 12, the U.S. Embassy in Colombo, Sri Lanka, called upon the Sri Lankan government to undertake an independent investigation and "seek the truth through independent and credible investigations, and where relevant, have prosecutions."

U.N. agencies estimated that more than 40,000 people belonging to ethnic minority Tamils died in May 2009 in the final stage of the war that ended with the decimation of the rebels from the Liberation Tigers of Tamil Elam, known as the LTTE, who had merged with fleeing civilians.

Beginning in 1983, the rebels carried out a violent campaign seeking autonomy for the Tamil majority in areas in the north and east of Sri Lanka. Overall, Tamils account for 18 percent of Sri Lanka's 20 million inhabitants. Sinhalese-speaking Buddhists account for 70 percent of the population.

"We had a general chat on the human rights concerns expressed by the people," Bishop Emmanuel told CNS.

The bishops maintained their stance despite calls from Sinhalese nationalist groups for the arrest of the bishops after they raised questions about war crimes with Rapp.

Bishop Emmanuel told CNS there are always adverse reactions "when we speak about unpleasant things."

"The man who needed to know was Mr. Rapp, and we had told him of our stand," Bishop Joseph told CNS.

In a media briefing after the meeting, Bishop Joseph said that even hospitals were attacked by the Sri Lankan forces and cluster bombs were used in areas crowded by fleeing Tamil civilians as a war tactic.

"A massive number of people were slain inside no-fire zones," he said. "Just because LTTE was also there, you can't execute a large number of civilians inside the NFZ. Even if the civilians were held as human shields, you can't justify killing civilians."

Bishop Joseph also alleged that a "structural genocide" was continuing in Tamil majority areas and that Tamil property was being appropriated by "government-aided colonization schemes."

"The international community should conduct an investigation to establish the truth. ... We are not asking this to make revenge on anyone in the government. We only want this for the betterment of this country," Bishop Joseph said.