Millions of Indians began voting Friday in the second round of multi-phase national elections as polarisation grows over Prime Minister Narendra Modi whipping up an assertive brand of Hindu nationalist politics in his campaign.

Voting opened at 7am in the country.

But turnout in the first round of voting last week dropped nearly four points to 66 percent from the last election in 2019, with speculation in Indian media that higher-than-average temperatures were to blame.

The second round of the poll -- conducted in phases to ease the immense logistical burden of staging an election in the world's most populous country -- includes districts that have this week seen temperatures above 40 degrees Celsius.

The outcome of Friday’s voting across 88 constituencies in 13 states with 160 million voters will be crucial for Modi’s Hindu nationalist Bharatiya Janata Party (BJP) as it includes some of its strongholds in states like Rajasthan, Madhya Pradesh, Uttar Pradesh and Maharashtra.

Most polls predict a win for Modi and the BJP, which is up against a broad opposition alliance led by the Indian National Congress and powerful regional parties.

Nearly 970 million voters will elect 543 members from a total 28 states to the lower house of Parliament for five years during the staggered election that runs until June 1.

The votes will be counted on June 4. (Agencies)