NEW DELHI: Indian activist Anna Hazare left jail Friday to start a two-week public fast likely to fuel an eruption of angry protests over corruption that has left the government stumbling for a response.

Thousands of frenzied, flag-waving supporters cheered the diminutive 74-year-old as he walked from the gates of Delhi's Tihar jail —his de-facto campaign headquarters since he was taken into police custody three days ago.

Smiling and waving, he led the ecstatic crowds in chants of “Hail Mother India” and vowed to pursue his hunger strike protest “until India is corruption-free”.

He then boarded an open-top truck to carry him through the streets to an open venue in central Delhi where he will stage his fast aimed at forcing the government to bow to his demands for stronger anti-corruption laws.

Once seen as just an annoying thorn in the side of the establishment, Hazare has transformed into a national figure whose popularity has destabilised a government elected in 2009 with an unassailable parliamentary majority.

His campaign has tapped into a deep reservoir of discontent —especially among India's burgeoning middle-class —with a culture that requires bribes to secure everything from business permits to birth certificates.

Hundreds of thousands have taken to the streets of cities across India in recent days in the most significant display of popular dissent for more than three decades.

The government's response, especially the initial arrest of Hazare and thousands of his supporters, has been widely criticised as a clumsy knee-jerk reaction from an administration that has lost touch with its electorate.

India's increasingly vulnerable-looking Prime Minister Manmohan Singh denounced Hazare's campaign as a “totally misconceived” attempt to undermine parliamentary democracy, but his words have gained little public traction.

Although officially released on Tuesday evening, Hazare had refused to leave his cell until the authorities lifted restrictions on what he had originally called an indefinite “fast unto death”.

In an embarrassing climbdown for Singh's Congress Party-led coalition, he was finally given permission to fast for 15 days in a large open venue normally reserved for religious festivals.

But in a fresh challenge to the authorities, Hazare said he was ready to push beyond that restriction as well.

“My health is fine,” he said in a video message released from his jail cell late Thursday.

“I feel I can fast beyond the 15 days permitted by the government. I shall seek permission to fast for another week. I will not stop fighting,” he said.