the photos shows Balachandran Prabakaran sitting in a bunker, alive and unharmed in the custody of Sri Lankan troops.
Another picture which was taken a few hours later shows the boy's body lying on the ground, his chest pierced by bullets.
Sri Lankan Army today dismissed as "lies, half truths, rumours and numerous forms of speculation" the pictures featured in the documentary.
Commenting on the pictures, military spokesman Brigadier Ruwan Wanigasooriya said, "This is not the first time such unsubstantiated allegations are leveled against the Sri Lankan forces. Interestingly, these come up as we near UNHRC meeting and die down thereafter."
"No substantive evidence have been presented for us to launch an investigation" he said.
"Unfortunately, it appears that the parties who float such baseless allegations never want these to be investigated or solved. They want to keep them as mysteries in order to tarnish the country's good image as and when it suits their agendas."
Wanigasooriya stressed that if the Channel 4 was interested in having these investigated, it should cooperate with credible evidence and the Army will institute a probe.
The documentary aims to test India over its next move in the UNHRC resolution against Sri Lanka, Channel 4's documentary director Callum Macrae said.
India had voted against Sri Lanka at last year's resolution.
"The new evidence in the film is certain to increase pressure on the Indian government not only to support a resolution on Sri Lanka and accountability, but also to ensure that it is robustly worded, and that it outlines an effective plan for international action to end impunity in Sri Lanka," Macrae said.
War crimes in Lanka: Human Rights Watch seeks UN intervention
New Delhi: The Human Rights Watch today sought a UN authorised independent, international investigation into war crimes that took place during the final months of the decades-long armed conflict in Sri Lanka.
In a letter to members of the United Nations Human Rights Council today, the organisation said probe should be authorised at the March 2013 session of the UN body.
Since the Council adopted a resolution on Sri Lanka at its March 2012 session calling for action, the Lankan government has