A U.N. expert called Tuesday for Sri Lanka to investigate and file charges against soldiers shown in a graphic video shooting bound, blindfolded prisoners and abusing corpses in the final days of the 1983-2009 civil war.

The expert, Christof Heyns, reviewed the 5-minute, 25-second video frame by frame with a team of technical and forensic specialists to determine its authenticity, and concluded that the video suggests there is enough evidence to open a war-crimes case. Sri Lanka has claimed the video is fake.

In the video, several men lie on a muddy track, bound and motionless. The camera cuts and another man is shown being forced to sit upright by a soldier in camouflage carrying a rifle. Another soldier steps up behind the seated prisoner and shoots him in the back of the head, point blank. The prisoner slumps sideways as the camera pans across the road revealing nine bodies, most of them naked, with gunshot wounds clearly visible despite the grainy quality of the footage.

The uniformed men then force another blindfolded prisoner down into the dirt. A gunshot rings out and he, too, jerks and collapses. Later, the camera focuses on a young man, his skull blown open. Soldiers stand over the half-dressed corpse of a woman, gloating.

Heyns, a South African law professor who is also the U.N.'s independent investigator on extrajudicial killings, said the footage provides solid evidence for a prosecution case.

"It's very rare that you have actual footage of people being killed," the former lawyer told The Associated Press. "This is different from CCTV. This is trophy footage."

The Sri Lankan government says the video is staged, an attempt by pro-Tamil Tiger groups to undermine its hard-won victory in the country's decades-old civil war.

"We have proven beyond any doubt that this is not authentic," the director general of the government's Media Center for National Security, Lakshman Hulugalla, said on Monday.

But Heyns says the video shows "definitive war crimes" and both domestic and international proceedings should be launched.

"There is a prima facie case and it should now go to the next level," Heyns told the AP before screening the video for the first time to reporters in Geneva. "So far we haven't seen any concrete results on the domestic level," he added.

If Sri Lanka resists outside pressure to conduct a credible criminal investigation, referral to the International Criminal Court would be possible, Heyns said. This is unlikely as it would require approval by the U.N. Security Council, where Sri Lanka has a strong ally in China.

The United Nations estimates that between 80,000 and 100,000 people were killed in the 26-year war. This includes at least 7,000 ethnic Tamil civilians killed in the last five months of the conflict. Numerous U.N.-appointed officials have concluded that both sides committed atrocities.

A recent U.N. report said Sri Lankan government forces deliberately targeted civilians and hospitals, and blocked food and medicine for hundreds of thousands of civilians trapped in the war zone. It also accused the Tamil Tigers of recruiting child soldiers and using civilians as human shields.

Sri Lanka has categorically rejected calls for an independent international probe into the allegations. Instead, it has established a national panel to investigate. Meanwhile, the government continues to celebrate its battlefield victory, hosting a three-day international defense seminar in Colombo this week to show foreign experts how it won the war.

The latest footage was obtained by Britain's Channel 4, which has so far shown only brief excerpts and an earlier, shorter video of the same events. Ben De Pear, head of foreign affairs for Channel 4 News, said the station chose to broadcast the footage after the U.N. experts helped it conclude that it is genuine.

The extended video will be part of an hourlong program examining atrocities committed by both government forces and Tamil Tiger fighters that Channel 4 plans to screen for the first time Friday at the United Nations in Geneva.


Ravi Nessman in New Delhi contributed to this report. Frank Jordans can be reached on Twitter at: http://twitter.com/wirereporter