Koirala, who was also president of the Nepali Congress (NC), died at his residence in Kathmandu’s Maharajgunj area.
Doctors told the media that he died at 12.50 a.m. due to failure of his respiratory system.
Koirala, who was the prime minister of Nepal from February 11, 2014, to October 10, 2015, will be remembered as the leader under whose leadership Nepal promulgated the new constitution through the constituent assembly in September 2015.
Koirala, who spent 16 years in India in exile during the pro-democracy movement in Nepal, was a survivor of tongue and lung cancers.
India condoled his death, with Prime Minister Narendra Modi saying “India lost a valued friend”.
“In Sushil Koirala ji, NC has lost a big leader who served Nepal for decades and India lost a valued friend. Pained by his demise. RIP.”
“Sushil Koirala ji’s simplicity holds lessons for all of us. My condolences to the Koirala family and people of Nepal in this hour of grief,” Modi said in a series of tweets.
Indian Home Minister Rajnath Singh also offered his tributes to Koirala. He said, “Nepal has lost a powerful voice and a wonderful human being”.
“He was Nepal’s one of the most seasoned politicians and also a true statesman.”
Koirala’s death comes a serious blow to the NC that is scheduled to hold its 13th general assembly in March 2016.
Hundreds of Nepali Congress leaders and supporters gathered at his Maharajgunj residence to offer condolence to the leader. NC senior leader and former prime minister Sher Bahadur Deuba said he was shocked by Koirala’s death.
Koirala, who was eyeing a second term as the party president, was known for his high integrity and simple lifestyle.