Indian social activist Anna Hazare's "fast unto death" is gathering support, after a minister quit a government panel on corruption when Mr Hazare questioned his credentials.
On Wednesday, Agriculture Minister Sharad Pawar said he no longer wished to be associated with the probe.
Protests and hunger strikes have been reported from other Indian cities.
Mr Hazare says he is fasting to pressure the government to enact comprehensive anti-corruption laws.
India has recently been hit by a string of high-profile corruption scandals.
The government has set up a committee to consider an anti-corruption bill, but Mr Hazare wants civil society included in the process. He says they should be part of a committee to draft the Jan Lokpal Bill (Citizen's Ombudsman Bill).
He has written a letter to Prime Minister Manmohan Singh asking him to "show courage" in tackling corruption. He also criticised ministers on the government corruption panel.
Almost 200 people, including various civil society activists, have joined the fast with Mr Hazare at the historic Jantar Mantar observatory in Delhi.
Correspondents say that Mr Hazare's fast has rallied people across the country disillusioned with the recent spate of scandals - he is highly respected as a social activist with an untarnished reputation.
On Thursday dozens of people marched in Delhi and there have been protests in Mumbai and Bangalore. On Wednesday night, his supporters held a candle-light vigil in Delhi while social activists held a "sit-in" demonstration at a Mahatma Gandhi statue in Lucknow in the northern state of Uttar Pradesh.
Bollywood stars, including superstar Aamir Khan, retired police officer Kiran Bedi, social reformist Swami Agnivesh and former cricketer Kapil Dev have also added their support to his cause.
The 72-year-old campaigner is on his third day of refusing all food until the government accedes to his demands.
Doctors are checking Mr Hazare twice a day to monitor his health.
"The fast is still on. Mr Hazare is in perfect health," Press Trust of India news agency quoted an aide as saying.
Alleged telecoms scam
In a letter to Prime Minister Manmohan Singh, Mr Hazare said that many members of the government's "group of ministers" on corruption "have such a shady past that if effective anti-corruption systems had been in place, some of them would have been behind bars".
Agriculture Minister Sharad Pawar quit the government panel after Mr Hazare criticised him in the letter.
"I have told the prime minister in writing about quitting the group of ministers on corruption," Mr Pawar told Press Trust of India.
"I have informed him that I don't want to remain anymore with the panel. I don't want to be associated with it. The chapter is closed from my side," he said.
Some of the recent corruption scandals to have rocked India include a multi-billion dollar alleged telecoms scam, alleged financial malpractices in connection with the Commonwealth Games, which India hosted, and allegations that houses for war widows were diverted to civil servants.
Last month the head of the country's anti-corruption watchdog was forced to resign by the Supreme Court on the grounds that he himself faced corruption charges.
Critics of the government say that recent scandals point to a pervasive culture of corruption in Mr Singh's administration - adding to the difficulties of a politician once seen as India's most honest.
The government denies the claims and has set up a parliamentary inquiry into corruption.
Last month a survey said corruption in India cost billions of dollars and threatened to derail growth.