Hazare, after his usual visit to Rajghat before any such protest in Delhi, came to the capital's dharna hotspot Jantar Mantar at around 11 am to loud cheers from tricolour-wielding anti-corruption supporters and chants of 'Vande Mataram' and 'Bharat Mata ki Jai'.
He is fasting to demand justice for slain IPS officer Narendra Kumar, murdered allegedly by mining mafia in Madhya Pradesh, and a strong law to protect whistleblowers.
Family members of some of the whistleblowers who were killed while fighting corruption, including that of Narendra Kumar, were also present.
Before starting his fast, Hazare said many people have sacrificed their lives while fighting corruption and the government has not conducted any probe despite some incidents which happened three years ago.
"Their (whistleblowers') mothers, their children, their fathers, their wives are crying for justice. But this government has gone dumb and deaf. It is not listening to the cries of people.
"There will be a big struggle. Then the government will listen. The government came up with MNREGA but these people were killed for trying to improve it," Hazare told reporters.
His return to staging protests comes after the Congress performed poorly in the recent assembly polls.
This will be the first hunger strike undertaken by the 74-year-old Hazare after he called off his three-day fast for a strong Lokpal Bill in Mumbai last December owing to failing health and poor response. This is the fifth time he is sitting on a fast in the past one year, of which four of them have been in Delhi.
Former Karnataka Lokayukta and Team Anna member Santosh Hegde, who had expressed some reservations with regard to the Team recently, was present along with other members like Shanti Bhushan, Arvind Kejriwal, Kiran Bedi and Manish Sisodia.
"Hazare has invited several families to be a part of one-day fast for a stronger whistleblower protection mechanism under the Jan Lokpal Bill," a Team Anna member said.
Setting the stage for Hazare's fast, Team Anna has put the blame on the ruling Congress for "sabotaging" the Jan Lokpal Bill, marking a departure from its stand of not targeting a single party.
At least 15 people, who tried to blow the lid on scams or fought the menace of corruption in other ways, have been killed since 2010, according to Team Anna.
These killings have brought to fore the need for a strong whistleblowers' protection system, under the control of the Jan Lokpal and Jan Lokayukta, it has said.
Attacking the Congress, it alleged, "The country knows it well that the Congress sabotaged the Jan Lokpal Bill meant to bring culprits to book in a speedy manner. If the Jan Lokpal would have been implemented, justice would not have remained elusive."
During the assembly elections, Team Anna had campaigned for a strong Lokpal though it had not named any single party.
However, Congress leaders had claimed that the tone and tenor of their campaign was anti-Congress.
Team Anna said while the Jan Lokpal ensure security to the whistleblowers, the proposed bill on the issue floated by the United Progressive alliance government is "inadequate and gives the responsibilities without powers to the Central Vigilance Commission."