The mercy petitions of the three convicts, two of whom are Sri Lankan Tamils, which had been with the President for over 10 years, were rejected early this month.
The authorities have set September 9 as the date for the hanging of Murugan, Santhan and Perarivalan, who have been convicted for the 1991 assassination of the former Prime Minister and the then Congress Party leader.
Murugan and Santhan are Sri Lankan Tamils. Senior Tamil National Alliance (TNA) MP Suresh Premachandran told PTI that his colleague S Sreetharan has written to the Indian President seeking clemency for the three.
Premachandran, however, did not detail the contents of the letter. Sreetharan is currently overseas. TNA was seen as the proxy-political party of the LTTE whose leader Velupillai Prabakaran was declared a wanted man by India for the killing.
India repeated their extradition request on Prabhakaran on an annual basis. Prabhakaran was killed in May 2009 during the last phase of the war against the LTTE.