Indians are voting in the first phase of a general election which pits the governing Congress party against the Hindu nationalist BJP opposition.
The nine-phase vote got under way in the north-eastern states of Assam and Tripura and will conclude on 12 May. Votes will be counted on 16 May.
More than 814 million Indians are eligible to vote in a poll dominated by corruption and high inflation.
An anti-corruption party the AAP offers another challenge to the main parties.
The Aam Aadmi (Common Man’s) Party) secured a spectacular result in local polls in Delhi last autumn and is fielding candidates in all of parliament’s 543 elected seats.
Several smaller regional parties are also in the fray and if no single party wins a clear majority, they could play a crucial role in government formation.
Brisk voting
India’s marathon vote is being staggered over more than a month for security and logistical reasons.
On the first day of voting, polling is taking place in six constituencies in two states in the north-east – five in Assam and one in Tripura.
Voters began queuing up outside the polling centres even before voting began in the morning, the BBC’s Sanjoy Majumder in Assam says.
A large number of the voters who turned up were women, dressed in colourful saris and some draped in Assamese shawls.
Many smiled happily after they had voted, holding up their fingers stained with indelible ink, a sign that they had exercised their right, our correspondent adds.
“We need good people in government,” said one of them.
Assam is a Congress party stronghold but the BJP is hoping to make inroads there.
The state is dotted with plantations growing the world-famous Assam tea and has more than six million eligible voters.
Brisk polling was registered in the state in the morning and by midday reports put turnout at about 35%.
The strong turnout is a sign, many believe, that voters are frustrated and want a change, our correspondent adds.
The main contest in the elections is between the Congress, led by Rahul Gandhi, the latest member of India’s influential Nehru-Gandhi dynasty, and the BJP, led by the charismatic and controversial Hindu nationalist leader Narendra Modi.
Mr Modi, who is ahead in all the pre-election surveys, is the leader of Gujarat state, which witnessed one of India’s worst anti-Muslim riots in 2002.
The BJP has promised to improve the economy and infrastructure and curb corruption if it wins in the general elections.
The party launched its manifesto hours after polling began for the first phase.
“Today the country has become stagnant. It is drowned in pessimism. It needs momentum to move forward,” Mr Modi said at the launch of the manifesto.
The Lok Sabha (lower house of parliament) has 543 elected seats and any party or a coalition needs a minimum of 272 MPs to form a government.
Some 814 million voters – 100 million more than at the last elections in 2009 – are eligible to vote at 930,000 polling stations, up from 830,000 polling stations in 2009.
Electronic voting machines will be used and will, for the first time, contain a None of the Above (Nota) button – an option for voters who do not want to cast their ballot for any of the candidates.
The Congress party has promised “inclusive growth” if it returns to power.
In its election manifesto, the party promised a raft of welfare schemes, including a right to healthcare for all and pensions for the aged and disabled.
Source: BBC News