Indian lambadi tribeswomen at a polling station in southern India [Source: BBC]

Tens of millions of Indians have voted on the first day of a general election that is being seen as a referendum on Prime Minister Narendra Modi.

Indians in 20 states and union territories cast their ballots in 91 areas.

The seven-phase vote to elect a new lower house of parliament will continue until May 19th and counting day is on May 23rd.

With 900 million eligible voters across the country, this is the largest election ever seen.

Some observers have billed the vote as the most important in decades and the tone of the campaign has been acrimonious.