Former RSS leader Tapan Ghosh, who had tested positive for COVID-19, died at a hospital on Sunday, his associates said.
Tapan Ghosh, 67, was the founder of Hindu Samhati group.
He was admitted to a private hospital last week after he tested positive for COVID-19.
"Tapan-da passed away this evening. He is survived by two sisters," Hindu Samhati president Debtanu Bhattacharya told PTI.
Tapan Ghosh is the second politician in the state to die due to COVID-19. Last month, Trinamool Congress MLA died due to the contagion.
Condoling Tapan Ghosh's death, senior BJP leader Swapan Dasgupta said he was one of the most dedicated persons fighting for the unity of Hindus in West Bengal.
"He gave his life to this cause, inspiring thousands through personal example. He will always be remembered and provide constant inspiration. Om Shanti," Mr Dasgupta, a Rajya Sabha MP, tweeted.
Tapan Ghosh died this evening. He was one of the most dedicated soldiers fighting for Hindu unity and sangathan in West Bengal. He gave his live to this cause, inspiring thousands through personal example. He will always be remembered and provide constant inspiration. Om Shanti— Swapan Dasgupta (@swapan55) July 12, 2020
Tapan Ghosh, who has been a pracharak of the RSS since 1975, broke away from the organisation in 2007, following some ideological differences.
Known for fiery speeches and often controversial remarks, he formed Hindu Samhati in 2008.
Formed with just a few hundred people, the organisation under his leadership spread to all districts of West Bengal, and also opened units in Jharkhand and Assam.
Tapan Ghosh left Hindu Samhati in 2018, following some differences within the outfit.