United Nations High Commissioner for Human Rights Louise Arbour is worried about shortcomings in the island's legal system and the fact recommendations from past inquiries have not been fully implemented, her office said.
The government announced on Monday the probe into a series of killings, including the assassination of the foreign minister and dozens of troops and civilians by suspected Tamil Tiger rebels, as well as the massacre of 17 aid workers which Nordic truce monitors have pinned on the security forces.
"It will be critically important for the commission to establish not only individual responsibility for crimes, but the broader patterns and context in which they occur," Arbour said in a statement issued in Geneva.
The government has invited foreign observers to assist in the year-long probe, which is mandated to investigate 15 major abuses since August 2005 as well as any other serious human rights violations it chooses.
"We want to get to the bottom of the truth," said Mahinda Samarasinghe, Minister for Disaster Management and Human Rights. "It is giving the country a bad image, it's not helping the situation as far as building confidence between the communities in this country.
"This is why we've opened it up to international observers."
More than 65,000 people have been killed in the conflict since 1983, including around 1,000 dead servicemen, around 500 civilians and an estimated 1,000 rebel fighters since December alone. Hundreds of civilians have been listed as "disappeared".
The first peace talks in eight months collapsed in late October over a rebel demand that the government reopen the main north-south highway which runs through Tiger territory to Jaffna, as each side accused the other of abuses.

Copyright Reuters, 2006