Tamil Nadu Chief Minister J. Jayalalithaa Wednesday described as "a war crime" the alleged cold-blooded killing of the son of the late Tamil Tigers' chief Velupillai Prabhakaran.

"The killing of Balachandran (Prabhakaran) is a war crime," the chief minister told the media here, and urged India to work with the US to pass a resolution in the UN denouncing rights violations in Sri lanka.

Jayalalithaa spoke a day after a section the media carried photographs of 12-year-old son Balachandran seated in a Sri lankan military bunker just before he was killed allegedly at close range.

The pictures are part of a film, "No Fire Zone", which seeks to document the widespread rights abuses during the final phase of Sri lanka's war when the military crushed the Tamil Tigers in May 2009.

Sri lanka has denied that Prabhakaran's son was killed in cold blood, and maintained that he died in crossfire with the liberation Tigers of Tamil Eelam (lTTE).

The chief minister said the young boy's killing was "unforgivable".

"I call upon the Indian government to hold discussions with the US and other like-minded nations and prepare a resolution to be passed by the UN (against Sri lanka)," she said.

She added that in line with a resolution passed by the Tamil Nadu assembly, India should impose an economic embargo on Sri lanka "with the cooperation of other countries".

The embargo should remain in place "until the Tamils who have been displaced there and confined in camps (after the conflict) are allowed to return to their homes and live with equal rights on par with" members of the majority Sinhalese community and "live a life of dignity".