GD Agarwal died due to a heart attack after being on a hunger strike for more than 100 days (India Today file photo)

GD Agarwal, a former professor at the Indian Institute of Technology in Kanpur and a man who devoted his life to the cause of saving river Ganga, died today. Agarwal was on a fast-unto-death. He died on the 111th day of fasting.

Agarwal began his fast on June 22 to protest the government's alleged inaction in taking measures to make the Ganga free of pollution and free-flowing.

Agarwal died at the All India Institute of Medical Sciences in Rishikesh where he was admitted by the Uttarakhand Police last night.

He suffered a cardiac arrest. He was administered a potassium and heart-related medicine intravenously when he was brought here: AIIMS Rishikesh on the death of GD Agarwal, who was on an indefinite fast in Haridwar since June 22 in a bid to urge the govt to clean river Ganga pic.twitter.com/on5atvEl8K ANI (@ANI) October 11, 2018

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Agarwal died due to a heart attack, the media coordinator of AIIMS Rishikesh said.

Prime Minister Narendra Modi said Agarwal's "passion towards learning, education, saving the environment, particularly Ganga cleaning will always be remembered".

Saddened by the demise of Shri GD Agarwal Ji. His passion towards learning, education, saving the environment, particularly Ganga cleaning will always be remembered. My condolences. Narendra Modi (@narendramodi) October 11, 2018

Agarwal, who took on the name Swami Gyan Swarup Sanand in his later life, went on a similar fast in 2012.

Then, his fast lasted nearly two-and-a-half months at the end of which the then Manmohan Singh-led government at the Centre was forced to give in to Agarwal's demand that a meeting of the National Ganga River Basin Authority (NGRBA) be held.

Agarwal, born in 1932 in Shanli, retired as a professor of environmental engineering from IIT Kanpur.

He served as a member-secretary of the Central Pollution Control Board.

In 2012, he formally renounced the world and adopted the name Swami Gyanswaroop Sanand.

(With inputs from Dilip Rathore in Dehradun)

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