Indian Prime Minister Narendra Modi's Bharatiya Janata Party is flush with cash, giving his Hindu nationalist bloc a massive advantage over the main opposition Congress party as he seeks to win a second term in India's general election.

Opaque campaign financing in the world's largest democracy makes it tricky to get a full picture of money in politics here. But current and former BJP supporters, opposition politicians, businessmen and activists interviewed say Modi has an unprecedented advantage, thanks to support from businesses and expectations he will be the winner.

Staggered voting in the general election is currently in progress across India, with results to be declared on May 23.