The head of India's "cockroach movement" has been detained as hundreds of protesters descended on New Delhi on Saturday.
The demonstration is the culmination of weeks of opposition mobilisation following allegations of misconduct during a nationwide voter-roll revision by the Election Commission of India (ECI).
The movement is demanding the election commissioner's resignation.
Cockroach Janta Party (CJP) founder Abhijeet Dipke and two other leaders were detained before disembarking from a flight in the capital, the group said.
It said in a statement they had been taken to "an undisclosed location".
"They're being denied access to their lawyers and cut off from all contact with others," the statement said.
RelatedOpposition parties and other critics say the voter-roll revision could disenfranchise millions of voters and benefit Prime Minister Narendra Modi's ruling Hindu nationalist Bharatiya Janata Party.
The ECI has rejected allegations of impropriety, saying the revision was intended to remove duplicate and ineligible voters.
Delhi has been under a strict security clampdown since Friday, with tens of thousands of police and paramilitary personnel deployed to stop those seeking to reach the main protest site in the heart of the city.
Authorities have closed dozens of metro stations, cancelled several trains coming to Delhi and temporarily shut down mobile internet around the protest site.
Dozens of protesters were taken away in police vehicles after they tried to march to the Jantar Mantar protest site in central Delhi, shouting anti-government slogans, AFP reporters saw.
The Hindu newspaper said as many as 3,000 protesters had been detained, although it was not immediately possible to verify that number.
