Chauhan, a dentist by profession who led the "Khalistan" campaign from London after leaving India, died last Wednesday of a heart attack at his home in Tanda in India's Punjab state, The New York Times reported quoting his wife.
The Times said Chauhan's separatist movement included a 1971 advertisement proclaiming the formation of Khalistan. The minority Sikhs constitute about 2 percent of India's population.
Chauhan faced sedition and other criminal charges in India.
The separatist movements led by Chauhan as well as Jarnail Singh Bhindranwale, who campaigned for a Sikh theocratic homeland, became violent in the 1980s and lasted a decade during which thousands died. The subsequent death of Bhindranwale in a military campaign in the Sikh holy city of Amritsar was blamed for the assassination of Indian Prime Minister Indira Gandhi in 1984.
With the death of Mrs. Gandhi, the Khalistan movement lost support. Chauhan returned to India in 2001 after a long court battle and ran a charitable hospital in Tanda, the report said.