NEW DELHI (AFP) - Voters went to the polls in India's capital on Saturday, with firebrand former chief minister Arvind Kejriwal looking to complete a surprise comeback and deliver the first major blow to Prime Minister Narendra Modi's premiership.

Less than a year on from his resignation as head of Delhi's state government after just 49 days, most polls say Kejriwal's anti-corruption party is set to push Mr Modi's Hindu nationalist Bharatiya Janata Party (BJP) into second place when results are announced Tuesday.

While polls have been badly wrong in the past, victory would be particularly sweet for the former taxman, who was trounced by Mr Modi when they both contested the parliamentary constituency of Varanasi in May's general election.

Most pundits had written off Mr Kejriwal, especially after his Aam Aadmi (Common Man) Party won just four seats in Parliament. But after apologising for leaving voters without an elected government for a year, Mr Kejriwal has been the star of the campaign, outshining former policewoman Kiran Bedi, who is the BJP's candidate for chief minister.

A steady stream of voters could be seen outside polling booths when they opened at 8am.

"People want a corruption-free and bribery-free Delhi and I'm hopeful they will vote accordingly," Mr Kejriwal told reporters as he went to vote.

"I am confident the people will win and that the truth will win."

Ms Bedi appeared equally upbeat, flashing a victory sign to photographers after she voted.

"Today the people of Delhi have to decide what kind of Delhi they want: do they want a city that is clean, safe and secure?," she said.

The BJP's campaign has been beset by divisions, with many activists cool towards the 65-year-old Bedi who has a history of disparaging the party.

A former reality TV show host, Ms Bedi is a seasoned media performer. But Kejriwal has proved his pulling power among working class and minority voters, with impromptu appearances drawing thousands.

Mr Kejriwal's campaign has been based around pledges to deliver lower utility bills and free wifi for Delhi's 17 million residents, as well as promising to counter corruption.

"Prices have gone up, water and electricity are becoming costlier. We need a government that brings some relief to the poor people," said 24-year-old Mr Pranav Singh as he voted in the southern Saket district.

Mr Kejriwal famously declared himself an anarchist during his brief tenure last year and staged several protests outside government offices.

He began in a blaze of glory, taking the metro to his inauguration and initially shunning his official residence. But his administration was soon mired in scandal, with a raid on a largely African neighbourhood sparking claims of racism.

In a press conference on Friday, Mr Modi's finance minister and top lieutenant Arun Jaitley said Aam Aadmi's rule had been "nightmarish".

"Delhi needs an administrator and not an anarchist," he said.

Rattled by Mr Kejriwal's popularity, Mr Modi himself has taken to the campaign trail, portraying his rival as a "backstabber" who betrayed voters last time round by quitting so early.

The BJP actually won most seats in the last election in December 2013, but surprisingly fell short of a majority, enabling Mr Kejriwal to form a government with the help of the centre-left Congress party.

It was the last real setback for the BJP, which has since stormed to victory in a string of state polls as well as the general election.

Defeat would not only signal the end of Mr Modi's extended honeymoon with voters, but also present him with a headache as Aam Aadmi is likely to try and stop his government pushing through reforms on issues such as land acquisition and foreign direct investment in the capital.

"It (Aam Aadmi) appears to be a credible challenger to the Modi juggernaut," said an editorial in The Hindu newspaper Saturday.

"The party's impressive revival after its rout in the parliamentary elections of May 2014 has put the BJP on the back foot and made Delhi the first real contest for Prime Minister Modi."

Polls close at 6pm, but the counting will not begin until Tuesday.