India has opened its polling stations for the biggest election the world has ever seen, which will not come to an end until 12 May.

With nearly 815 million people eligible to vote, India will vote in stages over the next five weeks in a staggered approach made necessary by the country's vast size.

Over 100 million people have been added to the voters' roll since the last general election in 2009. As many as 935,000 polling stations have been set up across the country.

polling booth
A woman casts her vote inside a booth at a polling station in Majuli, a large river island in the Brahmaputra river, Jorhat district, AssamReuters

Voting began in the remote northeastern states of Assam and Tripura. Several polling stations were temporarily closed while officials fixed or replaced faulty voting machines.

Elections in India are generally considered free and fair, but age-old traditions of caste loyalty, patriarchy and nepotism often influence voting patterns.

Women show their identification cards as they wait in line to vote outside a polling station in Koliabor, in Assam state's Nagoan districtAFP
Polling officers carrying electronic voting machines wait to board a boat to reach polling stations in Shikarighat, Jorhat district, in the northeastern Indian state of AssamReuters

Polls suggest the ruling Congress party could face a drubbing due to corruption scandals and economic slowdown over recent years. The opposition Bharatiya Janata Party and its candidate for prime minister, Narendra Modi, are seen as the biggest threats.

The election will be key to the future of the family dynasty that has ruled India for much of its post-independence history. The Nehru-Gandhi family is facing its biggest political threat in over a decade. Rahul Gandhi, the 43-year-old family scion, is seen as privileged, aloof and out of touch with everyday Indians.

Some sections see Modi, the chief minister of the western Indian state of Gujarat, as a divisive figure. They accuse him of turning a blind eye to the mass killings of Muslims in Gujarat in 2002.

spider man
Gaurav Sharma, an independent candidate also known as the Indian Spider-Man, poses as he arrives to register for the election in MumbaiReuters
Supporters hold up cut-outs of MK Stalin, son and heir apparent of M Karunanidhi, chief of DMK, during a rally in ChennaiReuters
india footballer
Baichung Bhutia, former captain of the Indian football team, signs a football during a rally. He is standing for the Trinamool Congress in the Darjeeling constituencyAFP
Amarinder Singh, former chief minister of the Punjab and now Congress Party candidate for Amritsar's parliamentary seat, addresses supporters during an election campaign rallyAFP
sonia gandhi
Sonia Gandhi, president of India's ruling Congress party, is showered with rose petals upon her arrival to register for the election in Rae Bareli in the northern Indian state of Uttar PradeshReuters
rahul gandhi
Rahul Gandhi, leader of India's ruling Congress Party, is embraced by a supporter at a rally in New DelhiGetty
Prime Ministerial candidate Narendra Modi poses with his BJP party manifesto in New Delhi. He pledged good governance as he released his party's delayed manifesto just hours after polls opened in the world's biggest election, which they are widely expected to winAFP

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

Results from all 935,000 polling stations are expected on 16 May.

rolling man
Raju Parekh, 51, a supporter of Hindu nationalist Narendra Modi, rolls along a road towards a temple in Ahmedabad. He said he planned to roll seven kilometres to appease Hindu goddess Kali and seek blessings for ModiReuters
sand sculpture
A sculpture by sand artist Sudarshan Patnaik depicts the Indian Parliament with various parties' election symbols, on a beach in Puri, in the eastern Indian state of OdishaReuters
A man sits in front of a mural depicting Indian political figures in KolkataReuters
modi rally
Supporters of India's main opposition Bharatiya Janata Party (BJP) attend a rally addressed by Gujarat's chief minister and Hindu nationalist Narendra Modi, in Guwahati, AssamReuters
modi mask
A supporter of Hindu nationalist Narendra Modi of the BJP, wears a Modi mask before the start of a rally in HiranagarReuters