India executed Mohammad Ajmal Kasab, the lone survivor of a fighter squad that killed 166 people in a rampage through the financial capital Mumbai in 2008, hanging him just days before the fourth anniversary of the attack.
Kasab, a Pakistan national, was the enduring image of the bloody assault, which traumatised India and raised fears of copycat attacks on foreign cities.
Pictures of the young gunman wearing a black T-shirt and toting an AK-47 rifle as he strode through Mumbai's train station were published around the world.
The hanging took place early on Wednesday amid great secrecy, underscoring the political sensitivity of the November 26, 2008, massacre, which still casts a pall over relations between nuclear-armed rivals Pakistan and India.
Al Jazeera's Sohail Rahman, reporting from New Delhi, said the execution happened very quickly for India's usually glacial justice system.
"The state of Maharashtra said they did not want him to be executed until there was a more conclusive summary of who was responsible for that attack."
Prisoners can often languish for years on death row but there had been a huge clamour for Kasab's execution.
India has executed just one person in 15 years - a former security guard hanged in 2004 for the rape and murder of a 14-year-old girl.
Kasab was buried inside the prison where he was hanged, officials said. India said it would hand over the body to Pakistan if a request was made.
"All the police officers and personnel who lost their life in the battle against the terrorists have today been served justice," Home Minister Sushil Kumar Shinde said shortly after Kasab was hanged in a jail in Pune, southeast of Mumbai.
There was relief on the streets of Mumbai as news of the execution swiftly spread.
"When I heard the news of Kasab's execution today, I remembered those horrifying moments of the attack. My eyes were filled with tears," said Vishnu Zende, who was working at Mumbai's train station on the day of the attack.
In August, India's Supreme Court upheld Kasab's 2010 death sentence over the attacks on a string of targets.
Nearly 60 people were shot dead in the train station alone. President Pranab Mukherjee rejected his plea for clemency on November 5, although this was not made public until Tuesday night.
Ten fighters arrived on the Mumbai shoreline in a dinghy on November 26, 2008, before splitting into four groups and embarking on a killing spree.
They held off elite commandos for up to 60 hours in two luxury hotels and a Jewish centre in the city.
India accuses Pakistan-based Lashkar-e-Taiba (LeT) of organising the attacks and says Islamabad is failing to act against those behind the raids.
Pakistan denies involvement and says it is prosecuting seven suspects for their role.
"Kasab was a foot soldier, the generals are in Islamabad, in Pakistan, and full justice will be done when they are brought to justice," Gopalapuram Parthasarathy, a former ambassador to Pakistan, told Reuters news agency.
Pakistan's Taliban movement expressed shock over India's execution of Kasab.
"There is no doubt that it's very shocking news and a big loss that a Muslim has been hanged on Indian soil,"
Taliban spokesman Ihsanullah Ihsan told Reuters.
A senior commander of LeT on Wednesday said Kasab was a "hero" who will inspire more attacks.
India and Pakistan's relations have gradually improved since the attacks, with progress made on trade and economic ties.
Possibly because of the planned execution, India on Tuesday asked Pakistan to postpone a visit this week by its Interior Minister Rehman Malik, saying the dates were "not suitable for us".
Malik was due to put the final seal on a deal to ease visa restriction for travellers.
Islamabad was informed beforehand about Kasab's execution, a Pakistani foreign ministry official who asked not to be identified said.
"If all judicial procedures were followed then the decision is acceptable," the official said.
Raju Ramachandran, one of Kasab's lawyers, said Kasab was a worried man when he last met him before the death sentence was upheld by the Supreme Court.
He was scared that he would be hanged and asked the lawyer, "Can you please help me get out of jail?"
During his appeal, Kasab argued that he was denied proper legal representation and that some charges against him were not proved beyond a reasonable doubt.
"I was denied a fair trial," Kasab said in a statement when his appeal hearing began in January. "I may be guilty of killing people and carrying out a terrorist act but I am not guilty of waging war against the state."