UN human rights investigator Philip Alston, who contended that the video is probably authentic, has called for a war crime investigation.
Alston made this claim based on reports by three US-based experts on forensic pathology, video analysis and firearm evidence, which 'strongly suggest that the video is authentic'.
However, Alston did not specify who should undertake the investigation into war crimes and other violations of human rights allegedly committed in Sri Lanka.
The video, which surfaced in Aug 2009, show execution of blindfolded and naked Tamils by Sri Lankan soldiers. The video had been reportedly shot by a Sri Lankan soldier in Jan 2009 using a mobile phone.
The Sri Lankan government, however, maintains that the video is fake.
The war against the Tamil Tigers ended in May 2009, with the death of the rebel chief V Prabhakaran.
During the several month long offensive as many as 7000 civilians were affected and hundreds of thousands of ethnic minority Tamil civilians were forced into refugee camps.