In total, about 714 million voters have been eligible to take part in the nationwide polls, which have been staggered over the course of a month for logistical and security reasons.
The first exit polls - banned during the staggered voting process - are expected hours after polling closes.
The counting of actual votes will then begin early on Saturday, with the final tally expected to be released later the same day or early on Sunday.
Al Jazeera's Barnaby Phillips, reporting from the state of Punjab, a relatively prosperous part of India with a predominantly Sikh population, said voters had turned up early, eager to cast their ballots.
But "there are also hardships in Punjab. We have been hearing how the terrible problem of farmers' suicides has spread to this part of India," he said.
"Many of these people have been telling us prices just keep on going up and up, and that they are sinking into debt. That going to affect how they vote.
"In the most recent election, the Punjab opted for the BJP [Bharatiya Janata party] and its allies.
"We do not have to wait too much longer now. On Saturday, the national electoral commission releases the results, not just from Punjab but from across the country, and we will finally know in what direction the Indian people have decided to go."
According to the Indian constitution, a new parliament must be in place by June 2.
Neither the ruling United Progressive Alliance (UPA) led by the Congress party, nor the main opposition National Democratic Alliance (NDA) headed by the Hindu-nationalist BJP, is expected to win enough seats to secure an absolute majority.
"Everything will depend on numbers"
Manmohan Singh, India's prime minister
The final verdict is therefore expected to trigger a frantic round of political horse-trading as the two main blocs scramble for new partners among a multitude of regional parties, all with their own local agendas.
"Everything will depend on numbers," Manmohan Singh, the Indian prime minister, said at a news briefing on Monday.
The Congress party, which has been in power for the past five years, has seen its main achievement of a spectacular economic growth hit by the global economic crisis.
The party also faces severe criticism for its handling of the Mumbai attacks in November, when 10 gunmen rampaged through the city, killing 166 people.
|The final results are expected to be released
over the weekend [AFP]
Nonetheless, Abhishek Manu Singhvi, a Congress party spokesman, said the party was confident of forming a coalition government.
"Whether individually or collectively we know very well how to conduct coalition ethics," he said, adding that they have the necessary experience to "do it successfully".
For its part, the BJP with its ageing and fragmented leadership has troubles of its own, including being blamed for stoking tensions between India's Hindu majority and large Muslim minority.
Many of the seats are expected to go to a range of regional and caste-based parties that tend to focus on local issues and promises, leaving India facing the prospect of a shaky coalition to govern its 1.1 billion people.
On Tuesday the Communist Party of India (Marxist) said it would decide on any post-poll alliance only after the final results are announced.
Sitaram Yechury, a senior party official, said they were busy campaigning on the ground and will consider future prospects after May 16.
The Communist party is part of an assortment of left-wing and regional parties that forged the "Third Front" on March 12 to challenge the ruling UPA and the main opposition NDA.
But observers say that whatever formation emerges it will most likely be an unwieldy coalition that will struggle to project a united front at a time when India is facing a sharp economic downturn and numerous foreign policy challenges.
"There is an absence of national leaders who are able to project the issues and enthuse people," Neerja Chowdhury, a political analyst, told the AFP news agency.
"There are no towering personalities to set an agenda for the nation."
Chowdhury said the party that usually emerges as the single largest is likely to form the government but added that there was "no guarantee" that would happen.
"Given the way the polity is divided and fractured, the grand prize is far away."