DEOBAND/ NEW DELHI:  Indians voted on Wednesday in the second round of a state election that is the biggest test of support for Prime Minister Narendra Modi since he rose to power three years ago, as controversy raged over the illegal publication of an exit poll.

The election, in Uttar Pradesh that is home to 220 million Indians, is the world's largest this year and will have a key influence on Modi's chances of clinching a second term as prime minister in 2019.

Modi's Bharatiya Janata Party (BJP) swept Uttar Pradesh in the 2014 general election on the way to winning the biggest national mandate in 30 years.

But the publication of an exit poll after the first round of voting in the state last Saturday has led to the arrest of a newspaper editor amid allegations that it amounted to an illegal attempt to influence voting in later rounds.

News organisations and survey groups conduct exit polls to glean the first pointers to the likely winner but the election commission bans their publication until all rounds of voting are completed.

Uttar Pradesh is holding seven round of voting, moving from west to east in a state more populous than Brazil, to allow security forces to redeploy and curb the risk of electoral violence or malpractice.

Shekhar Tripathi, an online editor with Hindi-language newspaper Dainik Jagran, told Reuters the criminal charges filed against him on suspicion of violating election rules were "baseless".

Final results on March 11 in Uttar Pradesh and four other state elections will deliver voters' first verdict on Modi's shock decision in November to withdraw 86 percent of the cash in circulation.

The banknote ban was launched to purge the economy of "black money", untaxed income and the proceeds of crime and corruption, but it has disrupted daily life and caused an economic slowdown.

On Wednesday, voters in 67 constituencies queued outside polling stations to elect lawmakers who will rule the impoverished state.

Modi's BJP hopes to defeat two heavyweight regional parties but will struggle to replicate its general election result, when it polled 42 percent of the vote and won 71 of 80 constituencies in the battleground state.

Voters' impatience has grown as Modi's promises of development failed to deliver new jobs in a state where an individual's average annual income runs less than $750.

In the town of Deoband, home to India's largest Islamic seminary, men and burqa-clad women queued outside mosques and schools to vote.

Rahim Raza, 34, said he was working as a daily wage labourer after Modi's note ban forced him to shut the shop he ran at a garage. "We should not vote for a party that destroyed our business," he added.