The Union government on Thursday moved the Supreme Court against Tamil Nadu chief minister J Jayalalithaa's move to free the killers of Rajiv Gandhi.
The apex court has agreed to hear the Centre's plea later in the day.
Remorseless killers of Rajiv Gandhi did not deserve remission of sentence, the Centre has said in its plea.
Centre has sought deletion of the last paragraph of the judgment which entitles the convicts remission of sentence.
Centre is also seeking a review of the judgment.
Meanwhile, Prime Minister Manmohan Singh has issued a statement slamming the move of Tamil Nadu government to free Rajiv Gandhi's killers.
TN govt's proposed course of action to release the killers of Shri Rajiv Gandhi is not legally tenable and should not be proceeded with, Manmohan Singh said in the statement, adding, the assassination of Shri Rajiv Gandhi was an attack on the soul of India.
Release of the killers of a former PM of India, our great leader, and other innocent Indians, would be contrary to all principles of justice. No government or party should be soft in our fight against terrorism, the Prime Minister said.
The Tamil Nadu government had on Wednesday announced to release all the seven killers in the Rajiv Gandhi assassination case.
It had given the Centre three days time to respond, failing which it said, it would go ahead and let all the seven convicts walk free.
The move by the state government came a day after the Supreme Court commuted the death sentence of three of the killers to life term.
A three-judge bench, led by Chief Justice P Sathasivam on Tuesday commuted the death sentences of Perarivalan, Murugan and Santhan, on the ground of a delay of nearly 11 years in deciding their mercy petitions by successive Presidents of India.
On Wednesday, Jayalalithaa said the state cabinet had decided to release the convicts as per the powers vested with the state under Section 432 CrPC.
It had decided to remit the sentences of Suthendraraja alias Santhan, V Sriharan alias Murugan and A G Perarivalan alias Arivu, considering the long incarceration of more than 23 years.
It has also decided to release immediately the other four convicts, Nalini, Robert Pyas, Jayakumar and Ravichandran, who served life-term for more than 23 years, she had said.
The Centre had reacted strongly to the state government's decision.
Congress vice-president Rahul Gandhi had expressed sadness over the state government's decision.
"If a Prime Minister's killers can be released, what kind of justice should the common man expect?" Rahul said reacting to the news.