Officials check Voter Verifiable Paper Audit Trail (VVPAT) machines in West Bengal [Source: Reuters]

Indians have begun voting in the first phase of a general election that is being seen as a referendum on Prime Minister Narendra Modi.

Tens of millions of Indians across 20 states and union territories will cast their votes in 91 constituencies.

The seven-phase vote to elect a new lower house of parliament will continue until 19 May. Counting day is 23 May.

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