Tens of millions of Indians voted Thursday in the second and largest stage of month-long general elections, with security forces on high alert for fresh attacks by Maoist rebels.

One week after the first round, polling stations opened in 12 Indian states with almost 200 million people eligible to vote on the day -- more than three times the population of France. The five-round vote wraps up May 13.

The polls come at a pivotal time for India and its 714 million electorate, with a once red-hot economy feeling the strain of the global downturn and relations with Pakistan at a new low since the Mumbai attacks in November.

With neither of the two main parties -- the incumbent Congress and the Hindu nationalist Bharatiya Janata Party (BJP) -- seen as capable of securing an absolute majority, the likely outcome is an unsteady coalition that would struggle to see out a full term.

In Amethi, the family stronghold of the Nehru-Gandhi dynasty in Uttar Pradesh state, voters queued early in one of the few races where the outcome was a foregone conclusion.

"Rahul will win, nobody else can win here," said first-time voter Mohammad Izhar, a teacher.

Rahul Gandhi, 38, the son of Congress president Sonia Gandhi, has been the party's star campaigner and is being groomed to follow his father Rajiv Gandhi, grandmother Indira Gandhi and great grandfather Jawaharlal Nehru as prime minister of the world's largest democracy.

Mohammad Zaki, 45, a labourer working in Saudi Arabia, timed his annual holiday to Amethi to coincide with the election.

"We're Congress loyalists. We'd win without my vote, but it's important to me," Zaki said.

Shortly after polls opened, a landmine blast triggered by suspected Maoists in the eastern state of Jharkhand injured a member of the security forces and two election officials.

The threat of extremist violence was highlighted Wednesday when Maoists briefly hijacked a train with several hundred passengers in Jharkhand.

The hostages were released but the incident underlined the rebels' ability to strike, seemingly at will.

Maoist attacks on polling stations during the first phase of voting last week claimed at least 19 lives, including 10 paramilitary troopers and five election workers.

The rebels, who say they are fighting for the rights of neglected tribal people and landless farmers, have been described by Prime Minister Manmohan Singh as the biggest overall threat to national stability.

The insurgency grew out of a peasant uprising in 1967 and has spread to more than half of India's 29 states.

More than two million security personnel have been deployed to keep the electoral process on track.

"We have foolproof security arrangements," said K. Rajendra Kumar, a senior police official in the troubled region of Kashmir, where troops ringed polling booths in the volatile Hindu-Muslim district of Udhampur that voted Thursday.

Many people say the health of the Indian economy is a major issue in the election.

After five successive years of near-double-digit growth which lent India the international clout it has long sought, the economy has been badly hit by the global downturn.

And there are major security concerns over growing regional instability, particularly arch-rival Pakistan, where the growing influence of the Taliban has been watched from New Delhi with increasing alarm.

But strong, decisive leadership will be difficult to provide given the splintered nature of the electorate, expected to hand up to 50 percent of the 543 seats in parliament to a plethora of local and regional parties.

For the Congress and the BJP, a realistic "victory" would mean emerging as the single largest bloc and using that to attract enough partners needed to govern.

Incumbent premier Singh, 76, is the Congress party's official candidate for prime minister and his main challenger is the BJP's L.K. Advani, who is 81.