814 million people are eligible to cast their votes , 100 million more than in the last elections in 2009.
State elections in Andhra Pradesh, Sikkim and Odisha will be held simultaneously.
The world’s biggest voting exercise pits the BJP’s Narendra Modi against Rahul Gandhi, who is leading the campaign of the Congress as the party asks voters for a third consecutive term in power.
Opinion polls have forecast that the BJP under Mr Modi will emerge as the largest party.
No single party has won a parliamentary majority since 1989 and the electorate has fractured in successive decades, turning regional leaders into powerful string-pullers.
The anti-corruption Aam Aadmi Party led by former tax inspector Arvind Kejriwal is likely to be seen as an unpredictable element in this year’s polls.
Just over a year since its formation, the party won enough seats in December’s Delhi state elections to take power for just under two months.
DATES OF VOTING
April 7, April 9, April 10, April 12, April 14, April 25, April 30, May 7, May 12.