A Kashmiri separatist has been executed over his role in a deadly attack on parliament in New Delhi in 2001, an episode that brought nuclear-armed India and Pakistan to the brink of war.
Mohammed Afzal Guru, a former fruit seller, was hanged at Tihar Jail on the outskirts of the capital on Saturday after his final appeal for mercy was rejected by President Pranab Mukherjee.
He is only the second person to be executed in India in nearly a decade.
With authorities fearing a backlash over the execution, a curfew was imposed in parts of Indian-administered Kashmir and the centre of the main city was sealed off.
While India's main opposition party welcomed the execution, one of Guru's co-accused who was later cleared said it was a travesty of justice.
"Afzal Guru was hanged at 8am. All legal procedures were followed in the execution," Home Minister Sushil Kumar Shinde told reporters.
"The situation in Kashmir is being closely monitored," he added.
A senior police officer at the jail told AFP that Guru had been woken up three hours before his execution after being held in solitary confinement.
Guru was found guilty of conspiring with and sheltering the militants who attacked the parliament in December 2001.
He was also held guilty of being a member of the banned Islamist group Jaish-e-Mohammed, which fights against Indian rule in the divided Himalayan region of Kashmir, where a separatist conflict has claimed up to 100,000 lives.
Five armed rebels stormed India's parliament in New Delhi on December 13, 2001, killing eight police officers and a gardener before they were shot dead by security forces. A journalist wounded in the attack died months later.
As the decision to hang Guru emerged, security forces imposed a curfew in rural areas parts of Indian-administered Kashmir, with the announcement made by loudhailer as police patrolled the Kashmir Valley.
Although there was no formal curfew order in Srinagar, police hastily erected barricades across main entry roads and in the city centre in a bid to prevent any possible demonstrations against the execution.
Three police helicopters could also be seen hovering overhead in Srinagar, the main city in what is India's only Muslim majority state.
A former chief minister of Kashmir once warned that executing him would lead the country to "go up in flames" because of a backlash from rebels in Indian Kashmir.
India alleged the militants behind the parliament attack were supported by Pakistani intelligence, leading the nuclear-armed rivals to deploy an estimated one million troops to their borders for eight months.
Guru's conviction, which has been delayed on several occasions, was both highly political and hotly contested. He described his imprisonment as a "gross miscarriage of justice" in his mercy appeal to the president.
A group of activists including lawyers have campaigned for him, saying his trial had major problems, including fabricated evidence presented by the police and the lack of proper legal representation.
Protesters against his "unfair" conviction have held regular demonstrations in Kashmir demanding his release, while right-wing Hindu activists have long demanded his execution to send a message to other potential attackers.
"Finally justice has been done but I want to ask the government what took them so long to reject his mercy plea and execute him," said Mukhtar Abbas Naqvi, one of the leaders of India's main opposition Bharatiya Janata Party.
Guru was initially convicted along with Shaukat Hussain, a former student at Delhi University and S.A.R. Geelani, a New Delhi college teacher, who were also handed the death sentence.
Geelani was freed on appeal after two-years of imprisonment, adding to the doubts about the initial trial.
Speaking after Saturday's execution, he said Guru never received a fair trial. "How can you send someone to the gallows?," he told AFP. "The whole process was flawed."
Executions are only carried out for "the rarest of rare" cases in India and Guru's is only the second since 2004.
The sole surviving gunman from the 2008 Mumbai attacks, Pakistani-born Mohammed Ajmal Kasab, was executed on November 21 last year.