He was 77. Bhandari is survived by his wife, a former parliamentarian, two daughters, and a son. He was the founder-leader of the Sikkim Sangram Parishad party.
Bhandari was in power in the tiny Himalayan state between 1979 and 1994 and the first Gorkha politician to lead an Indian state.
"Yes, our leader died today (Sunday) at the Primus hospital," a senior official posted at the Sikkim House said.
"He was admitted for a spinal problem. He underwent surgery a few days ago that was performed by Dr A.K. Jaishwar. However, he suffered cardiac arrest and died around 4.30 p.m.," the official said.
The body of Bhandari, one of the longest serving Chief Ministers in the country, will be taken to the All India Institute of Medical Sciences for embalming and later to Sikkim House.
Bhandari was born on October 5, 1940, in Malbasey village, near Soreng, in west Sikkim.
Bhandari began his political career in Darjeeling in 1967 by joining Tarun Sangha.
Once appointed as the party General Secretary in 1967 in Darjeeling, Bhandari later returned to his native place in Soreng, joined government service and started teaching.
He resigned from his job and joined Sikkim's pro-democracy movement. In 1974, Bhandari formed the Sikkim United Independent Front Party.
Later, he formed the Sikkim Janata Parishad in October 1977. Under his leadership, the party won 16 seats in the 1979 General Elections. He became the second Chief Minister of Sikkim on October 18, 1979.
In 1989, Bhandari's party won all seats in the assembly, again making him the Chief Minister for the third time.
He also briefly served as an Independent Member of Parliament from Sikkim in the 8th Lok Sabha.
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