An international rights group says a Sri Lankan government report on the country's recently-ended civil war “whitewashes” evidence of military atrocities against ethnic Tamils.

New York-based Human Rights Watch said Tuesday the Sri Lankan report is “another feeble attempt” to convince the world that government troops committed no crimes in their 2009 defeat of Tamil Tiger rebels after a 26-year long conflict.

The Sri Lankan defense ministry report released on Monday acknowledged for the first time that Sri Lankan soldiers may have killed civilians in the final phase of the war despite following a policy of “zero civilian casualties.” The report said it was impossible to avoid such casualties due to the magnitude of the fighting and what it called the “ruthlessness” of the government's Tamil rebel opponents.

The defense ministry gave no figure for the civilian casualties. Some rights groups say the number could be as high as 40,000, a figure rejected by Sri Lankan Defense Secretary Gotabhaya Rajapaksa on Monday as a “vague accusation” aimed at tarnishing Sri Lanka's image.

Human Rights Watch said the defense ministry report shows Colombo takes “no responsibility” for the civilian deaths. A U.N. panel of experts said earlier this year it found credible evidence that both government troops and Tamil rebels committed rights abuses, including possible war crimes, as the conflict ended.