Indians have begun voting in the world's biggest election, with the ruling Congress party pitted against the Hindu nationalist BJP opposition.

The nine-phase ballot begins on Monday and concludes on 12 May. Votes will be counted on 16 May, BBC reports.

More than 800 million Indians are eligible to vote in a poll dominated by corruption and high inflation.

A new anti-corruption party, the AAP, is also contesting the elections after a spectacular result in local polls.

The AAP (Aam Aadmi, or Common Man's Party) made a strong showing at the state assembly polls in the capital, Delhi, and is standing for all the seats in the parliament.

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.