The photos, part of a documentary for Britain's Channel 4, prove the Sri Lankan army's involvement in war crimes including summary execution and torture during the island's 37 year long civil war, according to director Callum Macrae.
The pictures 'tell a chilling story', Macrae wrote in an article published in the Indian newspaper The Hindu and the UK's The Independent.
In one, Balachandran, the youngest son of the slain Tamil Tiger leader, is seen eating a snack while sitting in a green sandbag bunker guarded by a soldier. A second image shows his bullet-riddled bare-chested body.
The documentary alleges that Balachandran was executed two hours after the first photo was taken. The images have been scrutinised by digital image analysts, who concluded they came from the same camera, and support video footage of the boy's body uncovered last year, Macrae said.
The Sri Lankan government has maintained that Prabhakaran's family were killed in fighting. The bodies of his wife and daughter have never been found.
"The new photographs are particularly important evidentially, because they prove that Balachandran was not killed in crossfire, or in a battle. His death was deliberate and calculated," Macrae wrote.
No War Zone: The Killing Fields of Sri Lanka will be released in March in Geneva to coincide with a UN Human Rights Council discussion on the country, currently facing censure by the US over its failure to probe war crimes.
Sri Lanka's military denied executing prisoners and accused the British network of engaging in a campaign to tar the country's reputation.
"These pictures come out in time for the UN Human Rights Council meetings. They want to discredit us," Sri Lankan military spokesman Brigadier Ruwan Wanisasooriya said. "No evidence has been presented to us to investigate." AFP