COLOMBO, Sri Lanka - The Sri Lankan government never seriously investigated reports of human rights abuses during 25 years of civil war and needs to rapidly overhaul its justice system to bring peace to the country, Amnesty International said Thursday.
  
The London-based rights group said the problem is even more urgent in the wake of the government's defeat of the Tamil Tiger rebels last month in a bloody offensive that the United Nations says left more than 7,000 civilians dead.

Human rights groups and diplomats accused the government of shelling heavily populated civilian areas and said the rebels held thousands of civilians as human shields, shooting those who tried to flee. Both sides denied the accusations.

"If communities that have been torn apart by decades of violence and impunity are to be reconciled, the Sri Lankan government should initiate internal reforms and seek international assistance to prevent ongoing violations and ensure real accountability for past abuses," said Sam Zarifi, Amnesty International's Asia-Pacific director.

In a report, the group called for the establishment of an international commission to investigate those allegations because past government probes into abuses have gone nowhere.

The government has repeatedly brushed off such calls, saying an international probe would interfere with the country's sovereignty.

Rajiva Wijesinha, secretary at the Ministry of Disaster Management and Human Rights, said the government's own commission of inquiry into a series of recent allegations of human rights abuses was proceeding, albeit slowly.

"These things take time, and we can't allow any possibility of injustice to happen," he said.

Last March, an international panel of experts established to advise the latest commission of inquiry resigned, saying the government lacked the political will to properly investigate alleged abuses, including the 2006 execution-style slaying of 17 aid workers for the French organization Action Against Hunger.

The Amnesty International report accuses the government of interfering with past investigations, by using bribes, threats and even murder to eliminate witnesses.

It said the vast majority of human rights violations are never investigated and those that are rarely end in convictions because hearings drag on, witnesses refuse to testify and in some cases even the prosecution does not show up.

At the same time, the country's human rights commission has been stripped of its authority, local rights activists have been threatened, the U.N. has been obstructed and the press has been stifled, the group said.

Meanwhile, a Japanese mediator said President Mahinda Rajapaksa promised to work for political and democratic reform in the country following the victory over the separatist rebels.

Yasushi Akashi said the president also told him Thursday that he would push for a political compromise with the country's Tamil minority to resolve the ethnic conflict.

Diplomats and aid workers have pushed for the government, dominated by the Sinhalese majority, to be magnanimous in victory or risk re-igniting the conflict.

They have also called for the swift resettling of nearly 300,000 ethnic Tamil civilians displaced by the fighting who are living in military-run camps in the north.

The aid group World Vision warned that the camps do not have adequate sanitation and the impending monsoon season could put tens of thousands at risk of diarrhea, cholera and mosquito-borne illnesses.

The group said at least 11,500 more latrines were needed to bring the camps up to international standards.

"When the rains come in two weeks or so, I can't imagine what conditions will be like due to the lack of any proper drainage and toilet system," said Suresh Bartlett, World Vision's country director.

Akashi said the camps were badly congested, had urgent sanitation problems and needed international assistance.