Rajiv Gandhi and 16 others including nine police officials were killed in Sriperumbadur on May 21, 1991 by a suicide-bomber strapped with powerful explosives.
"From the evidence, oral and documentary, the prosecution has established that conspiracy in this case was hatched by the LTTE supremo, V. Prabhakaran, Pottu Amman, chief of the intelligence wing of the LTTE, (and) woman`s wing deputy chief Akila in Jaffna and other places," the judge said.
"LTTE is not responsible for Mr Rajiv Gandhi`s killing," Anton Raja, an LTTE spokesman, told Reuters by telephone from London.
Twelve suspects -- including the man believed to have led the hit squad -- had committed suicide by swallowing cyanide to avoid being captured by police in 1992.
"The nation stands vindicated," says D.R. Karthikeyan, the federal police officer who led the investigation into Gandhi`s killing. He led a team of 180 officers who examined hundreds of thousands of documents, photographs and hours of videotape.
Judge V. Navaneetham`s judgement runs into 2,000 pages and comes six years after the assassination.
Congress spokeswoman Najma Heptullah said the verdict still fell short of uncovering an elaborate conspiracy. "The culprits were known. We all knew it was LTTE. But there was also a conspiracy behind it. That was to be uncovered...it has not been uncovered yet," she said.

A large section of the higher bureaucracy and members of the Indian intelligence/police community, however, believe that the LTTE was only the instrument for the assassination and that the direction came from some other organisation or individual.
They believe that LTTE chief Prabhakaran or someone equally high up in that terrorist organisation was offered a very lucrative deal to carry out the assassination. Several theories continue to do the rounds although there is no evidence to support any. One is that a section of leaders belonging to Rajiv Gandhi`s own party, the Congress(I), got together and through a third party arranged for his elimination. Mrs Sonia Gandhi`s statement that most of those who made Rajiv Gandhi`s assasination easy were still active in politics could be viewed in this context.