The vote pits Modi's Bharatiya Janata Party (BJP) against an alliance of two dozen opposition parties that promise greater affirmative action and more handouts while stressing what they call the need to save democratic institutions.

Three hours before polls closed on Friday, figures from the Election Commission showed voter turnout ranged between 40 per cent in the sprawling northern state of Bihar and 68 per cent in the small northeastern state of Tripura.

"Voters show great enthusiasm as polling reaches halfway mark," an election panel spokesperson had posted earlier on X.

"Substantial voter turnout reported."

The first of seven phases, Friday's vote covered 166 million voters in 102 constituencies across 21 states and territories, from Tamil Nadu in the south to Arunachal Pradesh on the Himalayan frontier with China.

Almost a billion people in the world's most populous nation are eligible to vote in the entire exercise running through the peak of summer until June 1, with results set for June 4.

"Modi will come back to power, because apart from the religious push, his other work, in areas such as safety and security, is good," said Abdul Sattar, 32, a Muslim voter in the city of Kairana in the most populous state of Uttar Pradesh.

Surveys suggest the BJP will easily win a majority, even though voters worry about unemployment, inflation and rural distress in the world's fastest-growing major economy.

Jobs were the chief concern for Mohammed Shabbir, another Muslim voter in Kairana.

None of his eight children had regular employment, the 60-year-old driver said.

"Even the Hindus are affected by a lack of jobs," he said, adding the problem outweighed the appeal of Hindu nationalism in the Hindu-majority nation.

Especially after Modi's January consecration of a grand temple to Lord Ram on a site in Uttar Pradesh believed to be his birthplace, Hindu nationalism is a key election theme.

Critics accuse Modi's government and party of targeting India's 200 million minority Muslims to please their hardline Hindu base - charges both deny.

Modi aims to win 370 of parliament's 543 seats, up from 303 in 2019, hoping for a two-thirds majority that some analysts and opposition members fear could let his party usher in far-reaching constitutional changes.

The BJP campaign focuses on Modi's guarantee to deliver on promises to voters.

"This election is not just to choose a member of parliament," Modi said on Friday.

"It is an election to secure the future of generations that come after you."

India needed a "strong" government at a time when "clouds of war are hanging over the world", he said.

Victory for Modi would make him only the second Indian prime minister to be elected three times in a row, after post-independence leader Jawaharlal Nehru.

Some BJP insiders and analysts say the party is worried about complacency or overconfidence among voters and party members, and needs to draw more people to vote.

The opposition's INDIA alliance has struggled to forge unity.

It has accused the government of hobbling its efforts by arresting its leaders in graft cases and making huge tax demands ahead of the vote - a charge the government denies.

The election would decide the future of Indian democracy, Rahul Gandhi, leader of the main opposition Congress party, said on X.

"Strengthen democracy by applying the balm of your vote to the wounds inflicted on the soul of the nation in the last 10 years ... defeat hatred," he said.

Australian Associated Press