The government executed Mohammed Afzal Guru on Saturday over his role in a deadly attack on Parliament in 2001 after his final mercy plea was rejected by President Pranab Mukherjee, officials said.
Mohammed Afzal Guru, a former fruit seller, was hanged at Tihar Jail at around 8am, becoming only the second person to be hanged in India in nearly a decade, officials said.
"Yes, he has been hanged," home secretary RK Singh said.
"President Pranab Mukherjee rejected Afzal Guru's mercy petition on Feb 3," Singh told reporters.
"My information is that he will be buried in the campus but it's the jail authorities who will go by jail manual," he said.
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.
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 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.
A journalist wounded in the attack died months later.
Sources in Srinagar said an emergency duty among all police officials was called in the morning and curfew has been imposed in Srinagar to stop any violent reaction.
Troops in large numbers have been fanned out in Kashmir valley. The government is tight lipped over which this step has been taken.
A year later, four accused, including Afzal Guru, were arrested for the attack and found guilty after a trial.
He and his wife filed mercy petitions to the President days ahead of being sent to the gallows in late 2006.
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 in Muslim-majority Kashmir have held demonstrations demanding his release, while right-wing Hindu activists have long demanded his execution to send a message to other potential attackers.
The widows of the police officers killed in the attack handed back their posthumous gallantry medals and said they would only take them back once Guru was sent to the gallows.
Guru was initially convicted along with Shaukat Hussain, a former student at Delhi University and SAR Geelani, a New Delhi college teacher, who were also handed the death sentence, reserved for the "rarest of rare" cases in India.
Their crimes were described as "horrendous, revolting and dastardly" by the Indian judge who tried them.
Guru's wife, Afsan Guru, who was found guilty of not disclosing information to police, was also sentenced to five years in prison but had her conviction overturned on appeal.
Geelani was also freed on appeal after two-years of imprisonment, adding to the doubts about the initial trial.
Executions are only carried out for extremely rare cases in India and Guru's would be 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.
Curfew in Kashmir
At least two persons were injured by security forces today in north Kashmir's Baramulla district when local residents came out to protest the hanging of Parliament attack convict Afzal Guru.
Residents in rural areas said police used loud hailers to order them to stay indoors from daybreak as it emerged that Mohammed Afzal Guru, a member of an Islamist group fighting Indian rule in the divided region, was to be hanged.
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.
Cable television service was also cut off from the Valley.
Authorities at the University of Kashmir in Srinagar meanwhile issued a statement announcing that examinations due to take place on Saturday had been cancelled.
BJP welcomes Afzal Guru's execution
BJP welcomed Guru's execution and said that it was a "much awaited and much wanted decision".
"This action is delayed. But undoubtedly it is a welcome action. ...it was a much awaited decision, much wanted decision so that the world could see that India is committed against terror, the fight against terror," BJP spokesman Rajiv Pratap Rudy told reporters.
He said the BJP has always been pressing for strong and prompt action against perpetrators of terror.
"Any action against terror like the hanging of Afzal Guru should be immediate. It cannot be delayed. If the highest court of the land upheld the conviction of Afzal Guru in 2007, thereafter there was no reason that any mercy petition should have been delayed for so long," he said.
"Though delayed, we still feel that the hanging of Afzal Guru was a right action. It has been done and the people of this country have been wanting and waiting for it for a long time," he said.
(With AFP, PTI inputs)