A UN report into the bloody end of Sri Lanka's civil war is due to be published, and could raise the question of an international war crimes inquiry. Channel 4 News submitted evidence to the UN.

Sri Lanka UN investigation report due to be published (Getty)

The report is expected to consider whether alleged atrocities committed by both sides at the end of Sri Lanka's 26-year civil war in 2009 constitute war crimes and deserve more international scrutiny.

Channel 4 News understands it could be published in the next ten days after UN Secretary General Ban Ki-Moon was presented with the report on Tuesday.

At least 20,000 civilians died in the final few months of the Government-led military campaign to crush the Tamil Tigers. There have been reports of the use of human shields and child soldiers and apparent executions, as well as deliberate shelling and denial of aid to civilians inside a no-fire zone.

The United Nations panel was set up in 2010 after pressure from human rights groups and western Governments, and after an initial UN investigation into the authenticity of what became known as the Channel 4 video - depicting the execution of a group of bound men in a muddy field in Sri Lanka - declared that video to be authentic.

Dr Kasipillai Manoharan's son was killed in Sri Lanka in 2006. He has been campaigning for justice and openness in Sri Lanka ever since. 

"I hope to see an international inquiry for this case but not just for this case, for all the young, all the civilians dead," he told Channel 4 News.

"That is what I am fighting for, in my life. Every politician, journalist, figure I meet, I tell them I want a judgement for my case. He was not political, he was a good sportsman, a good boy. I lost him. That's suffering. I want a judgement on this and I hope the UN will release their report - I have a right to see that report and so do all the civilians in Sri Lanka."

Read more on Dr Manoharan's five-year search for justice in Sri Lanka

The panel finished gathering evidence in December but its reach has been hampered by the Sri Lankan Government, which did not allow the panel into the country to collect evidence. The Sri Lankan Government set up its own - much criticised - investigation, the Lessons Learnt and Reconciliation Commission, to look at the war.

The Sri Lankan Government has hit out at the UN report, branding it "fundamentally flawed".

How the UN deals with Sri Lanka - given the scale and gravity of what happened there - it cannot be left to go unchecked. Amnesty International's Yolanda Foster

In a statement, the Sri Lankan Government said: "Among other deficiencies, the report is based on patently biased material which is presented without any verification."

Evidence

Towards the end of 2010, Channel 4 News obtained a longer version of the execution video, which was also sent to the UN panel led by former Indonesian Attorney-General, Marzuki Darusman.

An investigation into the video by this programme led to the identification of a woman journalist as one of the victims in the video, along with damning new details of the date and location where the video was filmed.

Watch the execution video below: please note that it includes some distressing images.

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Leading war crimes lawyer Julian Knowles of Matrix Chambers told Channel 4 News the Sri Lanka video was "astonishing evidence".

Depending on the conclusions of the UN report, UN Secretary General Ban Ki-Moon could order an investigation into alleged war crimes.

Read more on Sri Lanka's civil war in our Channel 4 News Special Report 

Justice

Yolanda Foster, Sri Lanka expert and researcher at Amnesty International, told Channel 4 News: "For Amnesty International, how the UN deals with Sri Lanka - given the scale and gravity of what happened there - it cannot be left to go unchecked.

"The UN can send a very important message to governments around the world - you cannot commit these violations."

She said Amnesty remains very concerned by ongoing human rights violations in Sri Lanka, including arbitrary detentions and reports of disappearances, and increasing pressure on human rights defenders.

"The panel is a good first step in setting out the widescale violations that occurred, but it is just the beginning. We very much hope that in the report there is a call to establish a UN commission inquiry to investigate the violations of international law which occurred."