Voters in India's remote northeast cast ballots on the first day of the world's biggest election Monday, with the opposition heading into the polls with strong momentum on promises of a surge in economic growth.

With 814 million eligible voters, India will vote in stages over the next five weeks in a staggered approach made necessary by the country's vast size. Voters will choose representatives for the 543-seat lower house of parliament.

Results from all 935,000 polling stations are expected on May 16. The opposition Bharatiya Janata Party and its candidate for prime minister, Narendra Modi, are seen as the biggest threats to the now-governing Congress party.

BJP is expected to do well but to fall short of a 272-seat majority, making a coalition government a likely outcome, observers say.

India election line

People line up to cast their vote outside a polling station in the northeastern Indian state of Assam. (Utpal Baruah/Reuters)

"I've made it a point to vote this time because we want change," said 36-year-old housewife Rumi Nath, waiting to vote in the rural town of Lakhimpur on the Brahmaputra River. "Our area remains backward and underdeveloped 67 years after independence."

Polls suggest Congress could face a drubbing due to corruption scandals and recent years of economic slowdown. The BJP's Modi has been credited with ushering in strong industrial growth in the western state of Gujarat, where he has been chief minister for 11 years.

The election will be key to the future of the family dynasty that has ruled India for much of its post-independence history.

Biggest threat in a decade

The Nehru-Gandhi family is facing its biggest political threat in over a decade, with Rahul Gandhi, the 43-year-old family scion, leading the Congress's struggling campaign. While Gandhi has been presented to voters as a youthful leader who can rejuvenate India's faltering economy, many see him as privileged, aloof and out of touch with everyday Indians.

The party has not even formally declared Gandhi as its candidate for prime minister, political maneuvering aimed at protecting him from being scapegoated if the party — and the family — is forced from power.

But even as Congress faces a backlash, critics of Modi question whether the Hindu nationalist candidate can be a truly secular leader, noting he has failed to take responsibility or apologize for communal rioting that left more than 1,000 dead in his state in 2002. He is accused of doing little to stop the anti-Muslim rampage, though he denies any wrongdoing and has never been charged with a crime.

'As monsoon sets in, we get worried about our daily meals.​'- Voter Pulok Nath on his election concerns

The BJP was the last major party on Monday to release its campaign manifesto, which envisions India's path toward full development through futuristic infrastructure projects such as high-speed trains, 100 new modern cities and wireless Internet facilities in public places.

But such ambitious plans hold little appeal for most voters in rural Assam, where voting took place Monday in five constituencies as well as in one in neighboring Tripura state.

Here, people are more concerned about basic needs like guarding against the dangers of flooding, soil erosion and heavy rains washing away homes, or building more roads and bridges to connect far-away towns and villages to the main cities.

"As monsoon sets in, we get worried about our daily meals," said Pulok Nath, a voter in Lakhimpur. "We have been living on a mud embankment for years now after floods washed away our home and large part of our village."

Turnout 74 per cent so far

Several of the 8,000 polling stations were temporarily closed while faulty voting machines were fixed or replaced. At the end of Monday's voting, officials said turnout for the first day of polling was 74 per cent.

Both Congress and BJP were hoping for a strong showing in the seven northeast states nicknamed the "Seven Sisters" — occupying a remote region nestled between China, Bhutan, Bangladesh and Burma and made up of diverse ethnicities. Gains for Congress among the 25 northeast seats would help offset expected losses elsewhere in India, while the BJP wants to seize one of Congress' traditional strongholds.

India election votes

A man votes in the northeastern Indian state of Assam on Monday. Hindu nationalist opposition candidate Narendra Modi is seen holding a strong lead on promises of economic revival and jobs, but is likely to fall short of a majority. (Adnan Abidi/Reuters)

Assam's highest elected official, Chief Minister Tarun Gogoi of the Congress Party, said he was confident of winning re-election.

"There is no Narendra Modi magic in Assam. The Congress has been winning every form of elections since 2001 in Assam, and we are going to repeat the performance this time," Gogoi said.

In the last general elections in 2009, Congress won seven of Assam's 14 parliamentary seats to the BJP's four, while regional parties won the rest.

Gogoi's 32-year-old son, running for office for his first time, said he was encouraged by the large number of politically engaged youths. With more than 65 per cent of India's 1.2 billion people being younger than 35, young voters are expected to have a strong impact on the election.

"I am extremely happy with the enthusiasm shown by the large number of young voters who have turned out to vote this time," Gaurav Gogoi said.