A coalition led by Indian opposition candidate Narendra Modi is set to win a majority of seats in the country's general election, an exit poll by research group C-Voter showed after voting closed.

Indians voted on the last day of a mammoth election as challenger Mr Modi sought a personal mandate in the holy city of Varanasi, crowning his campaign to rule the country with a mix of pro-business policies and Hindu nationalism.

Opinion polls almost unanimously predicted Mr Modi's Bharatiya Janata Party (BJP) will emerge as the largest party when votes are tallied on Friday to fill 543 seats in the Lok Sabha, or House of the People.

India's rupee surged and stocks set a record as investors bet Mr Modi will usher in a stable government focused on reviving Asia's third-largest economy.

"My brothers in Varanasi, let us vote peacefully, we are all one," Mr Modi said in a recorded address, appealing for calm after a heated campaign that was mostly peaceful but marred by several outbreaks of violence.   

Mr Modi is the first prime ministerial candidate to stand in Varanasi, a 3,000-year-old city built around the river Ganges where several religions mingle but that is best known for the Hindu belief that to die here allows souls to escape the cycle of reincarnation.

His choice of the city was widely seen as a bid to consolidate his credentials as part of the Hindu nationalist movement that sees India as primarily a Hindu country.

Mr Modi's critics see him as a hardliner even though he has campaigned mainly on his record of job creation and economic management.

The election was marred by massacres of Muslims in the remote state of Assam that political rivals tied to speeches by Mr Modi calling for illegal immigrants from Bangladesh to be expelled from India. The BJP has denied that the speeches were inflammatory.

Activists for the Communist Party in West Bengal state were injured by gunfire in clashes with a regional party during voting there, and crude bombs failed to explode after being thrown at a BJP candidate's Kolkata home, media reports said.

A triumph in Varanasi, in Uttar Pradesh state, would cap a gruelling, high-tech campaign by the 63-year-old chief minister of the industrialised state of Gujarat to lead the BJP back to power after a decade in opposition.

"Mr Modi is the prime mover of India - he can change the country," said Durgesh Kumar Gupta, 21, a geography student standing in a group of young men wearing bright orange T-shirts - the colour known as saffron in India and associated with Hinduism.

"We see the way he has changed Gujarat - many people from eastern Uttar Pradesh go to work there. Now he can change the picture of Varanasi and of India."

A string of scandals and a sharp economic slowdown have sapped the popularity of the ruling Congress party, which has promised to extend welfare policies that helped it win a second term five years ago.

"I am confident of giving a tough fight to Narendra Modi," its Varanasi candidate, Ajay Rai, told Reuters.

Buoyed by reports from the field in the rounds of voting already held, BJP leaders predict their party and its allies may win a record 300 seats, more than the 272 needed to secure an outright majority in parliament.

Market rumours that exit polls would point to a clear BJP victory sent Indian stocks to record highs.

The Indian rupee strengthened to a 10-month high on Monday, touching 59.51 per dollar. The broader NSE index breached 7,000 for the first time, up as much as 2.35%, while the benchmark BSE index rose as much as 2.52% to a life high.

However, polls falsely predicted that the BJP would win in 2004. India's bourse regulator has asked exchanges to test their systems to cope in case there is a sell-off on Tuesday.

If Mr Modi falls short, not only might he miss out on leadership, but India would also face uncertain negotiations to form a coalition government that - even if led by the BJP - could fall hostage to the demands of regional parties.