The latest stage of India's massive five-week election was marred by bloody violence Thursday, with a landmine triggered by Maoist insurgents killing at least five policemen in an insurgency-hit eastern state.

A polling official was also killed in the Muslim-majority Kashmir valley after militants ambushed his vehicle, as clashes and militant threats drove scores of local residents away from polling stations.

Elsewhere, constituents in the financial capital Mumbai, the home of Bollywood and sprawling slums, were among the 180 million eligible voters, as were residents of the electorally crucial southern state of Tamil Nadu.

The parliamentary election has been staggered in a bid to ensure the safety of the 814-million-strong electorate, with results due on May 16 when the opposition Bharatiya Janata Party (BJP) is forecast to take power.

In the eastern state of Jharkhand, Maoist rebels who have called for a boycott of the elections, killed five policemen in a landmine explosion as they were returning from polling duty.

"We can confirm that five of our brave men have died in the attack," head of Jharkhand police Rajeev Kumar told AFP.

The deaths underscored the security challenges facing election organisers in India which went to the polls on April 7.

- Low turnout -

Tension surged in the Muslim-majority Kashmir valley, where a separatist movement against Indian rule is centred, as police faced stone-throwing protesters in 20 different locations in Anantnag constituency, forcing them to use tear gas and batons to disperse the crowds.

Several journalists received minor injuries.

Voting was light at the heavily guarded polling stations after a campaign of intimidation by local militant groups, who killed three people this week and warned locals not to take part.

"I voted because if we send the right person to the Indian parliament he will raise our voice for azadi (freedom)," said defiant resident Umair, reflecting widespread separatist sentiment in the area.

Turnout was a mere 28 percent at 1800 IST (1230 GMT) the Election Commission said.

Very few in the picturesque Himalayan valley, surrounded by towering snow-capped mountains, were expected to support national election frontrunner Narendra Modi, a hardline Hindu nationalist who is leading campaigning for the BJP.

Modi, the chief minister of the western state of Gujarat, remains a divisive figure due to his association with anti-Muslim riots in 2002 shortly after he came to power. The unrest cost at least 1,000 lives.

The 63-year-old appeared before hundreds of thousands of cheering supporters on Thursday as he filed his nomination papers to contest a seat from the holy Hindu city of Varanasi in the northern state of Uttar Pradesh.

Dressed all in white, he was flanked by his controversial aide Amit Shah, who was briefly banned from campaigning for inflammatory comments he made this month in an area hit by anti-Muslim riots last year.

"This wave (in support of Modi) has been turned into a tsunami," Shah told reporters as Modi waved and bowed to the crowd, saying he felt "overwhelmed by the love of the people".

The streets were a sea of saffron, the BJP's colour which is associated with Hinduism, with the mainly male crowd decked out in BJP caps or carrying the party's lotus emblem flags.

Modi, elected four times in Gujarat, has steered clear of advancing his party's Hindu nationalist agenda on the campaign trail, presenting himself as a centrist economic reformer capable of delivering a clean government.

All polls show him as vastly more popular than his rival Rahul Gandhi from the scandal-racked ruling Congress party, which has been in power for 10 years but faces its heaviest ever defeat.

- Bollywood and business -

Millions of voters, from Bollywood stars and business leaders to slum dwellers, turned out in the western megacity of Mumbai, standing in queues in a rare show of social mixing.

The city's favourite son, cricket legend Sachin Tendulkar, voted early and urged others to follow suit.

"A wonderful start to my birthday, as a responsible citizen of our great nation," the 41-year-old wrote on Twitter accompanied by a "selfie" of his inked finger.

After a rather slow start, Mumbai saw a turnout of some 52 percent roughly an hour before polling closed at 1900 IST (1330 GMT).

The Bollywood movie industry turned unusually political last week after more than 50 filmmakers, actors and writers, many of them Muslim, signed an appeal urging Indians not to vote for Modi and instead choose a "secular" party.

Also going to the polls on Thursday were voters in Tamil Nadu state, where Chief Minister Jayalalithaa Jayaram is hoping to win enough support to play a pivotal role in shaping India's next government.

The former film star, known as "Mother" to her followers, is one of the country's powerful regional leaders who could play a kingmaker role if Modi fails to win a majority and needs coalition partners.

In all, constituencies in 12 states voted on Thursday including Assam, West Bengal, Chhattisgarh, Jharkhand, Madhya Pradesh, Uttar Pradesh, Bihar and Rajasthan.