The DMK supremo appealed to Sonia adding that Tamils across the country should be kept in mind considering the spirit of "forget and forgive".
"Congress which is heading the central government and its leader Sonia Gandhi should come forward to save the three lives," he said in a statement.
Keeping in mind that only few days were left, Karunanidhi said that both Tamil Nadu government and the Centre should come together and make efforts to save Murugan, Santhan and Perarivalan, who are be hanged on Sep 9 and whose clemency petitions were rejected by President Pratibha Patil recently.
"There is an emergent need for us to take all possibles efforts to save their lives on humanitarian ground and (in) the spirit of forget and forgive," he said.
He further said that the step was crucial in view of "appeals made by Tamils the world over"and also the three already spent 20 years in prison.
Earlier the three accused had appealed to the Jayalalithaa, CM to step in the matter. Various political parties also appealed for the death sentence of the three.