The fate of political heavyweights such as Narendra Modi, who is tipped to be the next prime minister, and Sonia Gandhi, leader of the Indian National Congress (INC), is to be sealed in the seventh phase of India's ongoing parliamentary elections.

Voting is taking place in 89 seats across seven states and two union territories in one of the key battles in the nine-phase, month-long democratic process.

In this round of polling, as many as 138 million people are eligible to cast their ballots and about 1,300 contestants are in the fray.

Both the incumbent INC and the main opposition Bharatiya Janata Party (BJP) have high stakes in this round.

The presidents of both the parties – Gandhi and Rajnath Singh o BJP – are contesting in today's (30 April) polling. Other top guns include BJP's senior leader LK Advani, the former chief minister of India-administered Kashmir Farooq Abdullah and BJP's key strategist Arun Jaitley.

Modi cast his vote in the Gandhi Nagar constituency of Gujarat state, where he has been chief minister for more than a decade.

After casting his vote, Modi said: "The BJP will form a stable government in Delhi soon. The Congress party has already conceded defeat... It is the end of the mother-son government," referring to Sonia Gandhi and her son Rahul, who is leading the campaign for the INC.

The first six phases saw polling in 349 of the 543 constituencies. The eighth stage of polling is on 7 May and the ninth and last phase of the gargantuan exercise is scheduled for 12 May, with the results expected to be announced on 16 May.

In total, there are 815 million people eligible to vote and the general election has been billed as the largest-ever democratic exercise in global history.