The 75-year-old wants Prime Minister Manmohan Singh’s government to strengthen a proposed anti-graft bill that he says doesn't go far enough and to investigate corruption allegations against more than a dozen Cabinet ministers.
The former truck driver said he would fast until death if the demands were not met, the Agence France-Presse reported.
"I am confident that... the people of my country will not let me die. I draw my strength and confidence from you," Hazare told several thousand supporters in New Delhi.
The Times of India said the elderly anti-corruption crusader had ignored warnings from his close aides against fasting again.
"My team had told me not to fast citing health reasons,” Hazare said.
“When over 400 people are on fast, I cannot ignore them and not be on fast. Yesterday also my team appealed to me not to fast but I am sitting on fast from now. I consider I have your permission.”
The proposed legislation was passed by the lower house of Parliament last year but is now stalled in the upper house.
Hazare’s campaign attracted huge crowds and round-the-clock television coverage last year, but interest in his fight against corruption has since waned.
But his die-hard supporters reject suggestions the protest movement is losing steam.
"This rally is not about numbers. Our strength should not be measured in how many people have come here. Our strength lies in our conviction and truth," Mitul Rana, 26, a software engineer, told AFP.
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