Indian prime minister Narendra Modi and his party have a commanding lead as votes are counted after a six-week general election, sending the stock market soaring in anticipation of another five-year term for the Hindu nationalist leader.

Election Commission data show the Bharatiya Janata Party leading in contests for 300 out of 542 seats in Parliament, with the Congress party ahead in 50 contests.

The data did not indicate what percentage of the estimated 600 million votes had been counted. The count is expected to conclude by Thursday evening.

India Elections
Narendra Modi (Manish Swarup/AP)

The election has been seen as a referendum on Mr Modi, whose economic reforms have had mixed results but whose popularity as a social underdog in India’s highly stratified society has endured.

Critics have said his Hindu-first platform risks exacerbating social tensions in the country of 1.3 billion people.

On the campaign trail, he presented himself as a self-made man with the confidence to cut red tape and unleash India’s economic potential, and labelled Congress party president Rahul Gandhi, the scion of a political dynasty that lost power in 2014, as an out-of-touch elite.

Rahul Gandhi
Rahul Gandhi (Altaf Qadri/AP)

Half a dozen exit polls released after voting concluded on Sunday showed Mr Modi and the Bharatiya Janata Party (BJP) winning. A party or coalition needs a simple majority, or 272 of the seats in parliament’s lower house, to govern.

“Mr Modi’s going to be the next prime minister, we are very assured of that,” said Meenakshi Lekhi, a member of parliament running for re-election in New Delhi.

Outside BJP headquarters in New Delhi, hundreds of people cheered and shouted party slogans, lifting cardboard cut-outs of Mr Modi and party president Amit Shah as other people played drums.

The BJP harnessed social media, including Twitter, where Mr Modi has the world’s second-highest number of followers, and WhatsApp to reach out to millions of supporters.

In the world’s largest democratic exercise, voters cast ballots on 40 million electronic voting machines, a method India began using 15 years ago after complaints that the manual count of paper ballots was tainted by fraud and abuse.

An election official checks electronic voting machines
An election official checks electronic voting machines (Manish Swarup/AP)

Losing candidates and political parties have raised doubts about the accuracy and reliability of the electronic method, noting the machines are not used in the UK, France, Germany, the Netherlands or the US.

The issue hit the headlines again this week. Top opposition leaders met Election Commission officials after videos appeared on social media showing some electronic voting machines being moved.

The party officials alleged the machines were being moved to be altered, but the commission said the images showed unused machines being moved into storage.

The machines print a paper slip each time a vote is cast that is locked inside a box. A small percentage of the boxes will be opened and the printouts checked against the computerised results.

The time it takes to count the paper ballots is expected to delay the results by several hours.