"This has been accomplished mostly by the actions of the LTTE linked groups, which have many trained LTTE cadres and operatives who are now fully engaged in propaganda activities," Rajapaksa told a seminar on post-conflict stability that had participants from about 25 countries.
The Liberation Tigers of Tamil Eelam is the official name of the Tamil rebels who were defeated by government troops in 2009, ending nearly 30 years of civil war. The Tigers were fighting to create an independent state for ethnic minority Tamils, saying they faced discrimination from the Sinhalese majority.
The groups referred to by Rajapaksa have accused the Sri Lankan government of killing ethnic Tamil civilians during the war and vowed to work to create self-determination and self-rule for Tamils in Sri Lanka's north and east regions, which they consider their traditional homeland.
A U.N. report says that as many as 40,000 people may have been killed in the final phase of the civil war, and Pillay's visit followed a resolution in the U.N Human Rights Council in March which called on Sri Lanka to investigate more alleged war crimes committed by government forces and Tamil rebels
Pillay, on Saturday, concluded a weeklong visit aimed assessing the rights situation in Sri Lanka, and her comments drew heavy criticism from the government which said she violated her mandate by making political comments.
The government said it was up to the Sri Lankan public to judge the country's leadership, rather than being "caricatured by external entities influenced by vested interests."
Pillay will report her findings to the council at the end of this month.
Separately, External Affairs Minister G.L. Peiris said Pillay's report "is indicative of a prejudiced mind and in no way shows the fairness and open-mindedness of an official undertaking of such a mission."
"What we find disturbing is the tone and substance of her report, the lack of fairness and balance," Peiris had reporters at the Sri Lankan Embassy in London on Monday, according to a statement released Tuesday by his ministry.