Mohammad Ajmal Amir Qasab, the sole surviving gunman from the 2008 Mumbai attacks, has been hanged.
The Pakistani national’s plea for mercy to Indian President Pranab Mukherjee was rejected earlier this month.
He was executed in prison in Pune early on Wednesday, the Home Ministry said.
The 60-hour siege of Mumbai began on 26 November 2008. Attacks on the railway station, luxury hotels and a Jewish cultural centre claimed 166 lives. Nine gunmen were also killed.
Qasab and an accomplice carried out the assault on the main railway station, killing 52 people.
He was convicted of murder and other crimes in May 2010. The Supreme Court upheld his death sentence in August.
‘Need for secrecy’
Maharashtra Home Minister RR Patil said Qasab was hanged in the Yerawada prison at 0730 (0200 GMT).
“This is a tribute to all innocent people and police officers who lost their lives in this heinous attack on our nation,” Mr Patil was quoted as telling reporters by the Associated Press news agency.
Qasab did not leave behind a will and was buried inside the jail, Maharashtra Chief Minister Prithviraj Chavan said.
Senior officials in Delhi said Qasab’s family members had been informed about the execution “through a letter sent by courier”.
In Delhi, federal Home Minister Sushil Kumar Shinde said he signed Qasab’s execution order on 7 November, two days after President Pranab Mukherjee rejected his clemency petition.
Qasab, who had been held in Mumbai’s Arthur Road jail, was moved to Pune’s Yerawada prison two days ago, Prithviraj Chavan said.
“We kept secrecy. It was important to maintain secrecy in this matter,” Mr Shinde said, adding that Pakistan had been informed of the execution.
The Indian government was under pressure to act against a man who carried out one of the deadliest attacks in the country, says the BBC’s Sanjoy Majumder in Delhi.
But the swiftness and secrecy in which the execution took place would have come as a surprise to many, our correspondent adds.
Commenting on Qasab’s execution, Pakistan’s Foreign Ministry spokesman Moazzam Ali Khan said: “We condemned terrorism in all its forms and manifestation… We are willing to co-operate and work closely with all countries of the region to eliminate the scourge of terrorism.”
But Pakistan-based banned militant group Lashkar-e-Taiba [LeT], which was blamed for the Mumbai attacks, hailed Qasab as a “hero”. He would “inspire other fighters to follow his path”, an unnamed LeT commander was quoted by Reuters as saying.
The Pakistani Taliban were “shocked” by the hanging, Reuters quoted Taliban spokesman Ihsanullah Ihsan as saying.
‘Help me get out of jail’
There has been no information yet on Qasab’s last few days, but his lawyer Raju Ramachandran, who argued his case in the Supreme Court, told Reuters that Qasab was a “worried man” when he last met him in August, before the court upheld his death sentence.
He was scared that he would be hanged and asked the lawyer: “Can you please help me get out of jail?”
Qasab was part of a 10-member group which arrived in Mumbai by sea on 26 November.
The men split into groups to attack various targets. Their siege of the Taj Hotel, Trident Hotel and a Jewish centre went on for more than two days.
Closed-circuit TV camera showed Qasab and an accomplice opening fire on passengers at one of Mumbai’s busiest train stations, Chhatrapati Shivaji Terminus.
Relations between India and Pakistan deteriorated sharply after India blamed Pakistan-based Lashkar-e-Taiba for the attacks.
After initial denials, Pakistan acknowledged that the assault had been partially planned on its territory and that Qasab was a Pakistani citizen. Ties have been gradually improving since then.
Qasab’s execution was the first in India since a man convicted of raping and killing a schoolgirl was hanged in the eastern city of Calcutta in 2004.