The UN Secretary-General is considering setting up an expert panel to look into alleged violations by the Sri Lankan army, after a report found a video showing prisoner executions "appears to be authentic".
The video released by Journalists For Democracy and obtained by Channel 4 News in August 2009, shows naked prisoners, blindfolded and sitting on the ground, being shot at close range.
When the images were first broadcast the High Commission of Sri Lanka immediately and categorically denied troops had taken part in atrocities against the Tamil community.
Officials from the country's government continued to maintain the soldiers had only been involved in fighting Liberation Tigers of Tamil Eelam (LTTE) rebels.
They said the video has been "doctored" to "defame the Sri Lankan government".
In September 2009, Sri Lankan officials said they had commissioned four separate investigations, and that they had "scientifically established beyond any doubt that this video is a fake".
This claim has now been refuted several times; by an independent video analysis expert, a forensic pathologist, and a firearms expert all cited by Special Rapporteur Philip Alston in his report commissioned by the UN.
He said: "Together, the reports by these experts strongly suggest that the video is authentic."
Mr Alston added that he hopes the UN Security Council and Secretary-General Ban Ki-moon take the assessment of the video footage seriously.
A spokesman for UN Secretary-General Ban Ki-moon has said a "full and impartial investigation is critical" but that an investigation into war crimes allegations should be handled by the office of the High Commissioner for Human Rights in Geneva.
Martin Nesirky says Mr Ban is considering setting up an expert panel that would advise him on the matter and "assist the (Sri Lankan) government in taking measures to address possible violations."
The Sri Lankan government has accused Mr Alston of "breaching diplomatic procedures".
Foreign Minister Rohitha Bogollagama has released a new statement. He said: "My Ministry has communicated in this regard both to the special rapporteur as well as to the UN secretariat in New York that the public statement is a violation of all the accepted procedures of the United Nations and the norms of justice and fair play."
He accuses Channel 4 News and the wider media of "a deliberate and sinister attempt to cause embarrassment and bring disrepute to the Government of Sri Lanka".
The row over the video's authenticity has been widely reported around the world. The Sri Lankan press is focusing on the latest rebuttal by the country's authorities. The headline in the Lanka times reads: Lanka slams Alston over remarks.
Human rights organisations have insisted an international inquiry is needed.http://www.channel4.com/news/articles/world/asia_pacific/sri+lanka+video+un+considers+violations/3493047