Indians voted in the crucial third phase of national elections, with millions going to the polls in the heartland states essential to the main opposition Hindu nationalist party's bid to end the 10-year rule of Congress party.

Suspected Maoist rebels, who have urged a boycott, briefly disrupted voting in their strongholds in eastern Bihar state and neighbouring Chhattisgarh, carrying out acts of violence despite thousands of security forces deployed in the area.

Nearly 110 million people were eligible to vote in the third phase of the elections in 92 constituencies in 11 of India's 28 states and three federally administered union territories. The multi-phase voting across the country runs until May 12, with results for the 543-seat lower house of Parliament announced on May 16.

Parts of sprawling Uttar Pradesh, Bihar, Chhattisgarh, Jharkhand, Haryana, Kerala, Madhya Pradesh and Maharashtra states were among the places holding balloting today.

Hours before the voting began, Maoist insurgents used a land mine to blow up a jeep carrying paramilitary soldiers, killing two and wounding three others and causing a suspension in voting in some parts of eastern Bihar state, police said.

Voting was suspended at 20 nearby polling stations but started as scheduled in other parts of Bihar state.

The insurgents struck again hours later and briefly disrupted voting in neighbouring Chhattisgarh state by firing at security forces guarding polling stations in Bastar district. There were no casualties and the rebels fled.

The main Hindu opposition, with strong momentum on promises of a surge in economic growth, appears to be leading the race to end the Congress party's 10 years in power.

Sonia Gandhi, the governing Congress party chief, and her son Rahul Gandhi, the party's vice president, voted in the Indian capital where their party was routed in a regional election in December.

Besides the Congress party and the opposition Bharatiya Janata Party, the vote is also crucial for the future of India's anti-corruption party, led by Arvind Kejriwal.

The Aam Admi Party, or Common Man's Party, scored a stunning upset in the New Delhi election, launching Mr Kejriwal to the national stage. He has led protests and hunger strikes to highlight his fight against government corruption over the past two years. The party is contesting nearly 400 parliamentary seats.

The threat of insurgent attacks is always a shadow over Indian elections, although voting in the northeast on Monday and Wednesday was mainly peaceful..