The police action came in front of hundreds of Hazare supporters who had gathered to back his "fast unto death" aimed at pressuring the government into strengthening a new anti-corruption law.[break]
"Plainclothes police came to the apartment where he was staying and asked him to accompany them peacefully," fellow activist Akhil Gogoi told AFP.
The 74-year-old devotee of independence hero Mahatma Gandhi was driven away in an unmarked car, Gogoi said.
Police sources said he had been picked up along with two other senior activists and taken to a police facility in north Delhi.
The supporters gathered at the apartment protested his detention, shouting anti-police and pro-Hazare slogans as he was taken away.
Gogoi said the remaining leaders of Hazare´s campaign would hold an emergency meeting "to decide on a future course of action".
Hazare had staged a 98-hour hunger strike in April that led to the government allowing him and his supporters to help draft the new anti-corruption law, called the "Lokpal" bill.
The April protest caught the country´s attention and was widely supported by celebrities at a time of growing anger over corruption after a string of scandals affecting federal and state ministers.
The proposed Lokpal bill creates a new ombudsman tasked with investigating and prosecuting politicians and bureaucrats, but Hazare wants the prime minister and higher judiciary to come under scrutiny.
Under the draft law, the premier and top judicial figures will be excluded.
Arguing that the law had been watered down, Hazare had planned to begin a second hunger strike in a New Delhi park on Tuesday.
Police banned the protest, arguing that the park was available for only three days and that Hazare had not given an undertaking to limit his fast to that time-frame.
Police had also asked him to ensure that no more than 5,000 supporters would gather at the protest site.
US State Department spokeswoman Victoria Nuland said last week that Washington counted on India "to exercise appropriate democratic restraint" when handling of anti-graft protests.
India rejected the statement as "needless" and said its constitution guaranteed freedom of expression.
"Those who don´t agree with this bill can put forward their views to parliament, political parties and even the press," premier Manmohan Singh said in his Independence Day speech on Monday.
"However, I also believe that they should not resort to hunger strikes and fasts unto death."
During his April strike, Hazare called for corrupt ministers to be hanged, telling a cheering crowd that "sometimes you need to resort to violence".
At least 1,200 detained in Indian crackdown: minister
Indian Home Minister P. Chidambaram said Tuesday that at least 1,200 people had been taken into custody in New Delhi as police acted to halt a hunger strike by a veteran anti-graft activist.
"A little over 1,200 or 1,300 people have been detained at different places," Chidambaram told reporters, adding that "we are not prohibiting a peaceful democratic protest".
He said the detentions had been due to protesters refusing to obey police conditions over the demonstration led by hunger striker Anna Hazare, who was among those held.
Police had told organisers that the high-profile rally at a public park in Delhi would be limited to 4-5,000 people and that it could only last three days.
Hazare´s planned protest was to pressure the government into strengthening a new anti-corruption law.
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