On death row for the brazen Mumbai terror attacks, its lone surviving perpetrator Ajmal Kasab has filed a mercy petition before the President, a fortnight after losing his legal battle for life in the Supreme Court.

The nearly four-year legal battle launched by Kasab had ended on August 29 when the Supreme Court upheld his conviction and death sentence in the 26/11 attacks case, saying he killed without "the slightest twinge of conscience."

"We have sent a mercy petition to the President filed by Kasab," a senior official at the high-security Arthur Road Jail where Kasab is lodged, told PTI, without divulging when the petition forwarded to the President.

The 25-year-old LeT operative had been given a certified copy of the Supreme Court verdict confirming his death sentence last week.

"Kasab was given certified copy of his death sentence confirmation verdict three days ago. One copy was given to him and the other was sent to the Supreme Court with his signature," an official of the Arthur Road Jail had said.

Asked if the Pakistani gunman, lodged in the bomb and bullet-proof egg-shaped cell, had been explained options before him, including moving a mercy plea, the official said Kasab was told about all procedures and rights he has as a convict, including moving a mercy petition.

166 people, including foreigners and policemen, were killed when Kasab and his nine accomplices let loose an orgy of violence at various Mumbai's landmarks including Hotel Taj and CST railway terminus on November 26, 2008.

While all other Pakistani terrorists perished in the counter-offensive launched by security forces, Kasab was captured alive.

According to a reply received under RTI, as many as 11 mercy petitions of death row convicts are pending before President Pranab Mukherjee.

While only the file related to Balwant Singh Rajoana, killer of former Punjab Chief Minister Beant Singh, is with the Home Ministry, 11 cases including that of Parliament attack accused Afzal Guru are with Rashtrapati Bhavan.

The reply provided to activist Subhash Agrawal shows that Home Ministry had recalled 26 mercy petition from Rashtrapati Bhavan during 2009-12 to review its advice.

After the files were resubmitted, the then President Pratibha Patil had decided 18 cases. The remaining eight cases are still with the President's office.

The reply shows three mercy petitions, including that of Afzal Guru, have been submitted before the President for decision.