"Had young leader Rajiv Gandhi been alive today, that noble man would have definitely come forward to save the lives of Santhan, Perarivalan and Murugan, responding to the voice of true Tamils and in accordance with the golden saying of Anna, ''forget and forgive", he said in a statement.
The DMK patriarch had urged Gandhi last week to intervene on the issue, saying appeals by Tamils across the world needed to be considered in the spirit of "forget and forgive".
Fervently appealing to the Centre and state government to save the lives of the three from the "clutches of death", he said capital punishment imposed on them should be cancelled.
"If this is done, the entire Tamil race will extol such humanitarian action and they will be happy", he said.
Karunanidhi said he knew persons on whom capital punishment was imposed who were "pursuing a constructive way of life" after their sentences were commuted and they were released.
He himself had been responsible for some of those prisoners being released, he said, adding, "On this basis, I fervently appeal to the Central and State governments to save the lives of the three youths from the clutches of death, taking this not as an epistle, but as a mercy petition".
Apparently taking a dig at Jayalalithaa, Karunanidhi said that when "Tamil Eelam'' (separate nation in Sri Lanka) freedom fighters and innocent Tamils were attacked and killed by the Sinhalese Army, we did not remain silent, saying that such things are quite common in war".