Mohammad Afzal Guru, the Kashmiri militant sentenced to death over a 2001 plot to attack India’s parliament, has been hanged after his final clemency plea was rejected.
Officials said Mohammad Afzal Guru, who had been on death row since 2002, was executed at Tihar jail near Delhi.
Afzal Guru had always denied plotting the attack, which left 14 dead.
India has stepped up security and announced a curfew in Indian-administered Kashmir, where news of the execution was expected to spark unrest.
Executions are very rare in India – Afzal Guru’s was only the second since 2004, after Mohammed Ajmal Kasab, the sole surviving attacker from the 2008 Mumbai attack was executed in November.
“This is only about the law taking its course,” Home Secretary RK Singh said.
Hundreds of police and paramilitary personnel have been deployed in towns and cities across Indian-administered Kashmir to try to contain any unrest sparked by the execution.
Claimed in its entirety by both India and Pakistan, Kashmir has been a flashpoint for more than 60 years and two wars have been fought over it.
Mohammad Afzal Guru, the Kashmiri militant sentenced to death over a 2001 plot to attack India’s parliament, has been hanged after his final clemency plea was rejected
The December 2001 attack was one of the most controversial incidents in recent Indian history, correspondents say.
Five rebels stormed India’s parliament in Delhi on December 13, 2001, killing a gardener and eight policemen before they were shot dead by security forces.
India blamed the attack on the Jaish-e-Mohammed militant group, which it said was backed by Pakistan.
Pakistan denied involvement in the attack but relations between the two countries nosedived as their armies massed about a million troops along the border.
Mohammad Afzal Guru, a former fruit seller, was one of two men sentenced to death for helping to plan the attack, although the sentence of Shaukat Hussain was later reduced on appeal to 10 years in jail.
He was found guilty of arranging weapons for the attackers and of membership of Jaish-e-Mohammed, both of which he denied.
Two other people accused in the case, SAR Geelani and Afsan Guru, were acquitted due to a lack of evidence.
Mohammad Afzal Guru’s appeal was first refused by the Supreme Court and then the president.
India and Pakistan have exchanged fire across the Line of Control in the disputed Kashmir region.
Pakistan said Indian troops had raided a military post in the Haji Pir sector of Pakistani-administered Kashmir, killing a soldier and injuring another.
An Indian army spokesman said Pakistan had “initiated unprovoked firing” at Indian military posts.
Kashmir is claimed by both nations in its entirety and has been a flashpoint between them for more than 60 years.
Exchanges are not uncommon but rarely result in fatalities.
The Pakistani military’s public relations office said the two sides were still exchanging fire in the area.
It said Indian troops had “physically raided a checkpost named Sawan Patra”.
India and Pakistan have exchanged fire across the Line of Control in the disputed Kashmir region
The Haji Pir Pass is just south of the main road from Muzaffarabad in Pakistan-controlled Kashmir to Srinagar in Indian-administered Kashmir.
“Pakistan army troops effectively responded to the attack,” it said, adding that Indian troops had left behind weapons as they retreated.
Colonel Brijesh Pandey, a spokesman for the Indian army in Kashmir, told the Associated Press news agency that Pakistani troops had “initiated unprovoked firing” with mortar shells and automatic weapons at Indian military posts. One civilian home was destroyed, he said.
“We retaliated only using small arms. We believe it was clearly an attempt on their part to facilitate infiltration of militants,” Col. Brijesh Pandey said.
There has been a ceasefire in Kashmir since late 2003.
India suspended a peace process with Pakistan following attacks by Pakistan-based militants in Mumbai in 2008. Negotiations resumed in February last year.
Last month, the nations signed an agreement to ease visa restrictions on travel for some citizens.
President Asif Ali Zardari has arrived in India for the first visit there by a Pakistani head of state for seven years.
Asif Ali Zardari was met at Delhi’s Palam air force base by India’s parliamentary affairs minister Pawan Kumar Bansal.
Pakistani president is having lunch with Indian Prime Minister Manmohan Singh, before travelling to an important Muslim shrine in Rajasthan.
It is hoped the meeting could boost economic ties between the two nations.
Asif Ali Zardari is officially coming for private religious reasons, to visit the shrine of Sufi saint Moinudin Chishti in Ajmer, 350 kilometres (220 miles) southwest of Delhi.
However, his Interior Minister Rehman Malik and son and political heir Bilawal Bhutto Zardari are reportedly among an entourage of at least 25 people who have travelled with him.
President Asif Ali Zardari has arrived in India for the first visit there by a Pakistani head of state for seven years
Asif Ali Zardari was driven from the air base to the Indian prime minister’s residence amid tight security.
The two men were to meet privately before sitting down for lunch.
The focus of their talks is likely to be on issues that they can reach agreement on, such as trade.
One Indian government source told Reuters news agency the “prime minister will talk only about issues related to trade, education and culture this time”.
Relations between Pakistan and India have been gradually improving since peace talks were derailed after the Mumbai attacks in 2008.
Asif Ali Zardari recently backed the lifting of trade restrictions on India, and Pakistan is also talking of dropping a restrictive list of what products it will buy from India.
But tensions remain over more sensitive issues, such as the disputed region of Kashmir, and Pakistani militant activity against India.
Only this week, India again called for Pakistan to hand over Hafiz Saeed, the man it alleges planned the Mumbai attacks, after Washington announced a $10 million bounty for his arrest.
Pakistan has again refused, asking to see proof for the allegations.
The last time a Pakistani leader met Manmohan Singh was in 2005 when then Pakistan President Pervez Musharraf happened to be at the same cricket match as the Indian prime minister in Delhi.
The shrine of Sufi saint Moinudin Chishti is one of the most popular pilgrimage sites in the region, receiving a constant flow of devotees.