UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein accused Colombo of subjecting civil society groups and rights activists to surveillance, harassment and other forms of intimidation.
"A wall of fear has been created that has undoubtedly served to deter people from submitting evidence," he said in a statement.
The UN Human Rights Council last March ordered an international investigation into allegations that up to 40,000 ethnic Tamil civilians were killed by government troops in the final months of fighting in the civil war, which ended in 2009.
Sri Lanka, which denies any civilian was killed by its security forces, has repeatedly refused to cooperate with the probe, insisting a domestic commission of inquiry can do the job.
Zeid questioned that, pointing out that "since the end of the conflict in 2009, Sri Lanka has continued to obstruct any independent investigation despite the persistent, compelling and widespread allegations that possible serious international crimes were committed by both sides."
He said Sri Lanka was not only not cooperating with the investigation ordered by the UN's top human rights body but was "continuing (a) campaign of distortion and disinformation".
The government was also trying "to prevent possible bona fide witnesses from submitting information to the investigating team," he said, describing it as "an affront."
"The government of Sri Lanka has refused point blank to cooperate with the investigation despite being explicitly requested by the Human Rights Council to do so," he said.
This snub did not undermine the probe but rather "raises concerns about the integrity of the government in question."
"Why would governments with nothing to hide go to such extraordinary lengths to sabotage an impartial international investigation?" he said.
The Sri Lankan government charged earlier this week that the probe had been "unprofessional" and that its approach was "selective and biased" -- accusations Zeid flatly rejected.
Zeid also rejected as "absurd" charges that the probe had been compromised by allegations that a man was arrested in possession of blank signed forms that could be fraudulently filled in and submitted to investigators.
"It is a false equation to suggest that because someone may have been trying to submit false submissions, the inquiry is discredited," he said, insisting "we don't accept anything at face value."
The UN has estimated up to 100,000 people may have been killed in the separatist conflict between 1972 and 2009.
COMMENTS (1)
Comments are moderated and generally will be posted if they are on-topic and not abusive.
For more information, please see our Comments FAQ
The UN has become a Puppet on a chain organization. Like the Major Powers it only acts against the weak and poor nations. What has it done about the Palestinian genocide, Myanmar killings, etc.