Announcing Vajpayee's passing in a New Delhi clinic Thursday, India's current prime minister Narenda Modi said his predecessor had "set the foundations for a strong, prosperous and inclusive India in the 21st century."
"Atal Ji's passing away is a personal and irreplaceable loss for me," Modi said, using a Hindi-language honorific for Vajpayyee.
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The former premier died at the All India Institute of Medical Sciences (AIIMS) in Delhi, where he was admitted nine weeks ago. He had suffered a stroke in 2009.
"Unfortunately, his condition deteriorated over the last 36 hours and he was put on life support systems. Despite the best efforts, we have lost him today," AIIMS said in a statement.
Foundations laid for BJP
Vajpayee, a former journalist and poet-turned-politician and sometimes described as a moderate Hindu nationalist, was widely credited with helping lay the foundations for the rise of the Bharatiya Janata Party (BJP), which stoked fears of India's Muslim minority.
He led the BJP to its first national electoral victory in 1996, but lasted just 13 days as prime minister before he resigned in the face of a no-confidence motion.
He returned to power in 1998 for 11 months after forging an alliance of 22 parties, and went on to ordered nuclear testing that prompted international alarm over the possibility of war between India and Pakistan. Islamabad responded with its own tests.
Despite clashes in the disputed Himalalayan region of Kashmir, Vajpayee resisted military pressure to widen the conflict.
In February 1999, he led a groundbreaking bus ride to Lahore, Pakistan, where he met with its then-prime minister Nawaz Sharif. That diplomatic journey inaugurated the first regular bus service between the two nations.
Vajpayee last served as India's prime minister from 1999 to 2004.
Blamed over Gujarat anti-Muslim riots
Critics excoriated Vajpayee or failing to quell anti-Muslim riots that Gujarat state in 2002. More than 1,100 people, mostly Muslim, were killed. The riots began in a train fire that killed 60 Hindu pilgrims.
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Shortly before leaving office, he launched a peace process with Pakistan that, while often rocky, still underpins negotiations on the sub-continent.
As a parliamentarian, Vajpayee would take his dogs for walks. He never married, but lived with his adopted daughter, her husband and their daughter.
India's highest civilian award was made to Vajpayee in 2015.
ipj/rc (AP, AFP, dpa, Reuters)