India will elect a new parliament in seven phases between April 19 and early June, the country's election authority said on Saturday, in what amounts to the world's largest election with nearly one billion eligible to vote.

The election pits two-term Prime Minister Narendra Modi and his regional allies against an alliance of two dozen opposition parties, with surveys suggesting a comfortable win for Modi's Hindu nationalist Bharatiya Janata party (BJP).

A victory would make Modi, 73, only the second prime minister after Jawaharlal Nehru, India's independence hero and its first prime minister, to win a third straight term.

"We address you at a precious moment, when we as a nation are set to reiterate our pledge to electoral democracy, when Indians will together express their will once again," Rajiv Kumar, the head of the independent Election Commission of India, told reporters.

The last of the seven phases of voting will be held on June 1 and votes counted on June 4, he said.

Modi said the "biggest festival of democracy" had started and his party would campaign on its track record of "good governance and public service".

"I have full confidence that we will get the full affection and blessings" of more than 960 million voters for the third consecutive time, he said in a series of posts on X.

Modi and his party have been in campaign mode for months. The prime minister has been flying around the country almost daily, inaugurating new projects, taking part in religious events and addressing public and private meetings.

In his speeches, Modi has been showcasing India's economic growth, with India becoming the fastest-growing major economy in the world at present, as well as investment in infrastructure and welfare programmes for the poor.

Modi will be challenged by an alliance of some two-dozen opposition parties led by the main opposition Congress party called INDIA or the Indian National Developmental Inclusive Alliance.

The alliance formed last year has, however, been struggling to stay united and share seats amicably. (Reuters)