Parliament House attack convict Afzal Guru was hanged till death on Saturday morning in Tihar jail over his role in the 2011 Parliament attack.
The hanging took place at around 8 am in complete secrecy with only few people like home minister Sushil Kumar Shinde knowing about the operation.
Guru's final mercy plea was rejected by President Pranab Mukherjee on February 3, according to officials.
"Yes, he has been hanged," home secretary R.K. Singh said. "President Pranab Mukherjee rejected Afzal Guru's mercy petition on February 3," Singh told reporters.
Guru was found guilty of conspiring with and sheltering the militants who attacked the Parliament in December 2001, an incident that brought nuclear-armed India and Pakistan to the brink of war.
Five armed rebels stormed the Parliament complex in New Delhi on December 13, 2001, killing eight police officers and a gardener before they were shot dead by security forces.