Canada should mount a domestic search for Sri Lankan war criminals and lean hard on the South Asian country to submit to an outside probe of atrocities on both sides during the last months of its war against the Tamil Tigers, says a global conflict-prevention group led by Canadian Louise Arbour.

In a report released Monday, a year after the war's end, the International Crisis Group cited "reasonable grounds to believe the Sri Lankan security forces committed war crimes" by intentionally shelling civilians, hospitals and humanitarian operations in a final push to destroy the separatist Tigers. In turn, the Tigers reportedly shot civilians who tried to flee rebel areas and held others captive in a bid to raise international pressure for a ceasefire.

The Brussels-based group, funded by donors and governments including Canada's to study armed conflict and how to avert it, called for a United Nations-backed inquiry to account for a Sri Lankan government victory over the Tigers that came "at the cost of immense civilian suffering and an acute challenge to the laws of war."

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Canada, the United States, India and other countries with significant Sri Lankan populations should insist on such a probe, the group said, and impose sanctions on Sri Lanka - which is not a member of the International Criminal Court - unless it complies.

"I would like to see Canada encourage the [UN]secretary-general to launch an international investigation," Ms. Arbour, the crisis group's president and former chief prosecutor for the International Criminal Tribunals for the Balkans and Rwanda, told The Globe and Mail.

Ms. Arbour, a former Supreme Court of Canada justice, added that Canada "should not hesitate to exercise its universal jurisdiction" to prosecute Sri Lankan war crimes and human-rights abuses if suspects surface here. While 33,485 people identified themselves as Sri Lankan in the 2006 census, Canada is said to be home to about 200,000 Sri Lankan Tamils, the largest such group in the world outside Asia, many of whom supported the Tigers' 26-year insurgency.

A Department of Foreign Affairs spokesman did not respond to the report, but in an e-mail to The Globe, Alain Cacchione wrote that "Canada has consistently registered its governance and human rights concerns" during the conflict. He added that Canada expects "a viable political solution" to address all Sri Lankans' hopes, and that it will support the country's efforts "to promote national reconciliation and reconstruction within a united Sri Lanka."

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Bob Rae, the Liberal foreign affairs critic who worked with the Sri Lankan government and the Tigers during past peace efforts, said the widely respected crisis group's "significant" findings deserve a fuller response from the Conservative government.

"The efforts by the Sri Lankan government for reconciliation have not exactly been overwhelming to this point," said Mr. Rae, who was denied entry to Sri Lanka as a "security threat" before he could observe conditions at displaced-persons camps last June. "It's going to take more than these bromides from the Government of Canada to get to the bottom of things."

Ms. Arbour said an investigation is necessary to deter other countries from adopting "the Sri Lankan option" - unrestrained military action, refusal to negotiate and disregard for humanitarian concerns - to quell insurgencies. A full accounting is also essential for Sri Lankans, and for diaspora Tamils in places like Canada, to move on peacefully, she said.

"We really believe that unless there's accountability for what happened, there is no chance - no chance - of a lasting peace in Sri Lanka," Ms. Arbour said.

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Chitranganee Wagiswara, Sri Lanka's High Commissioner to Canada in Ottawa, reserved comment on the report until she hears from her government in Colombo. "These are allegations that have been made and they stand as allegations at the moment," Ms. Wagiswara said.

David Poopalapillai, spokesman for the Canadian Tamil Congress, said he was "very happy" the report called for an independent inquiry, as Tamils have demanded since before the war ended. "Our cries have been vindicated," he said.