In April, UN Secretary-General Ban Ki-moon published a report by a UN-appointed panel of experts, which concluded that as many as 40,000 people were killed in the final weeks of the war between the Tamil Tigers and government forces.

Now Channel 4's Jon Snow presents a forensic investigation into the final weeks of the war with "devastating new video evidence of war crimes - some of the most horrific footage Channel 4 has ever broadcast":

Captured on mobile phones, both by Tamils under attack and government soldiers as war trophies, the disturbing footage shows: the extra-judicial executions of prisoners; the aftermath of targeted shelling of civilian camps; and dead female Tamil fighters who appear to have been raped or sexually assaulted, abused and murdered.

This film provides powerful evidence that will lend new urgency to the panel's call for an international inquiry to be mounted, including harrowing interviews with eye-witnesses, new photographic stills, official Sri Lankan army video footage, and satellite imagery.

Watch at Channel 4