COLOMBO, Sri Lanka — A government-appointed commission concluded Sri Lanka's military did not intentionally target civilians at the end of the country's civil war and that ethnic rebels routinely violated international humanitarian law.

The conclusions from the Lessons Learnt and Reconciliation Commission report, which was presented to Parliament on Friday, contradict an extensive U.N. report that accused the government of deliberately shelling civilian areas and possibly killing tens of thousands of people in the final months of the conflict.

Human rights groups and the U.N. experts panel have called for an international war crimes probe, arguing that the government could not be expected to conduct a credible investigation of its own behavior during the conflict, which ended in May 2009.

The government commission said some isolated allegations of civilian abuses by security forces needed to be investigated further, suggesting that any violations could only have resulted from soldiers who were not following orders.

The government is expected to argue that the report makes an international investigation unneccessary.

The commission gathered evidence from ethnic minority Tamils, government officials, politicians, civil and religious leaders and former rebels. International rights groups refused to testify before it, saying it was pro-government, did not have a mandate to investigate abuses and did not meet international standards.

The report listed allegations by witnesses that the navy had killed civilians who tried to escape the war by boat and that the army had forced civilians to retrieve the body of a dead soldier amid a hail of fire and had shot to death those refused to comply.

"In these circumstances the commission stresses that there is a duty on the part of the state to ascertain more fully the circumstances under which such incidents could have occurred, and if such investigations disclose wrongful conduct, to prosecute and punish the wrong doers," it said.

The commission, however, said it found no evidence of deliberate killings of civilians in "no-fire zones" set up in the final months of the war.

"On consideration of all facts and circumstances before it, the commission concludes that the security forces had not deliberately targeted the civilians in the NFZs, although civilian casualties had in fact occurred in the course of crossfire," it said.

The commission also said it had serious doubts about the authenticity of a video broadcast by Britain's Channel 4 television which purportedly showed soldiers shooting bound, blindfolded prisoners and abusing corpses.

Christof Heyns, the U.N. independent investigator on extrajudicial killings, has said the video is authentic and provides enough evidence to open a war crimes case.

The commission's report, which was earlier presented to President Mahinda Rajapaksa, said the defeated Tamil Tiger rebels disregarded international humanitarian law in their combat strategies, and urged tough legal action against rebels being held in detention.

It accused the rebels of using civilians as human shields, killing civilians trying to escape the fighting, conscripting child soldiers, laying land mines, and using civilians as forced laborers.

Human rights groups have long accused both the government and Tamil Tiger rebels of abuses. A U.N. panel reported in April that it found credible allegations against both sides of abuses that could amount to war crimes. It accused the government of deliberately shelling civilians and hospitals and of blocking food and medical supplies for people trapped in the war zone. It said tens of thousands of civilians may have been killed in the final phase of the war and called for an independent international investigation.

The commission acknowledged that shells did fall on hospitals and cause casualties, but said there was no evidence to prove who had fired them.

It said the government had taken all possible steps to deliver food and other supplies to the war zone, although at certain times there were acute shortages.

After insisting for more than two years that not a single civilian had been killed by military strikes during the war, the government in August admitted to civilian deaths for the first time. Last month Defense Secretary Gotabhaya Rajapaksa, the president's brother, announced that the government has started a count of its own to ascertain how many civilians were slain.