"Birthday greetings to our beloved Atal ji. We salute this great personality who provided exceptional leadership to India at a crucial time.
"Be it as a party leader, parliamentarian, minister, prime minister, Atal ji distinguished himself in every role. This is his speciality," the prime minister said in a series of tweets.
Modi said he would pay a visit to the Bharatiya Janata Party stalwart later in the day.
"After landing in Delhi this evening, will head straight to Atal ji's residence and wish him personally."