The investigation into the 1991 assassination of former prime minister Rajiv Gandhi is the subject of a Bollywood thriller which promises to reveal new facts about the suicide attack, a report said on Tuesday.

Gandhi was killed by a suicide bomber while he was on his way to address an election meeting in Sriperumbudur near Chennai. The assassination was blamed on Sri Lanka's LTTE.

It was seen as revenge for Gandhi sending Indian soldiers to Sri Lanka as peacekeepers but who eventually got embroiled in the bloody ethnic conflict there.

"It will be a celluloid investigation of Rajiv Gandhi's assassination and tackling questions that were never asked," director Anubhav Sinha was quoted by a national daily.

The film will not dwell much on Gandhi's life and will start with his death. But Sinha still wants to rope in a big Bollywood star like Abhishek Bachchan or Sanjay Dutt to portray the slain leader.

A special court sentenced 26 people, including some Sri Lankans, to death for the assassination, but Supreme Court upheld capital punishment for only four of them in 1999.

One of them – a young mother – has since received presidential pardon while clemency appeals of the rest are pending.