DIBRUGARH: Indians began voting in the world's biggest election Monday which is set to sweep the Hindu nationalist opposition to power at a time of low growth, anger about corruption and warnings about religious unrest.

Voting began at 7:00 am (0130 GMT) in six constituencies in tea-growing and insurgency-wracked areas of the northeast, an often neglected part of the country wedged between Bangladesh, China and Myanmar.

"I want the government to reduce poverty and do something for the future of my children," said 30-year-old tea plantation worker Santoshi Bhumej at a polling station in Dibrugarh in the state of Assam.

The marathon contest, to be held over nine phases until May 12, got under way after a bad-tempered campaign which reached new levels of bitterness at the weekend.

Religious tensions, an undercurrent to the contest which has mostly focused on development until now, burst into the open on Friday when the closest aide of Modi was accused of inciting sentiments.

Amit Shah faces a judicial investigation after he reportedly told supporters to see the election as "revenge" against a "government that protects and gives compensation to those who killed Hindus".

Rahul Gandhi, leading Congress into his first national election as scion of the famous dynasty, used the comments to underline his message that a victory for Modi threatens India's religious fabric.

"Wherever these people (the opposition BJP) go they create fights. They'll pit Hindus and Muslims against each other," he warned on Sunday.

The BJP said talk of "revenge" was normal ahead of an election and said the other remarks were taken out of context.

Prime ministerial front-runner Modi, the hawkish son of a tea seller whose rise has split his party, is a polarising figure due to his links to anti-Muslim religious riots in 2002.

He urged voters on Sunday to give him a majority in the 543-seat parliament in defiance of surveys which repeatedly show the BJP are likely to need coalition partners when results are published on May 16.

"I need your blessings for a strong government and strong government means not less than 300 Lok Sabha (lower house of parliament) seats," he said.

The party released its delayed manifesto later on Monday which included core Hindu nationalist policies such as building a temple for the god Ram on a disputed religious site in northern India and protecting cows.

Disgruntled voters

In Assam, a Congress stronghold, some disgruntled voters told AFP they had been swayed by Modi's promises of better infrastructure, strong leadership, jobs and a clean administration.

"The current Congress government is corrupt. They have not been able to control rising prices in the country. I believe that Modi will give us a corruption-free government," local voter Deepa Borgohain told AFP.

Despite a decade under Congress when growth has averaged 7.6 per cent per year, a sharp slowdown since 2012 has crippled the public finances and led investment to crash.

Coupled with a widespread perception that Prime Minister Manmohan Singh's second term was largely lost to indecision and scandal, Modi has been able to tap into a groundswell of discontent.

The election will be the biggest in history and is a mind-boggling feat of organisation as voters travel to nearly a million polling stations.

In 2009, officials walked for four days through snow to deliver voting machines in the Himalayas, while yaks, camels and even elephants were pressed into action elsewhere in the vast country.

Such is India's population growth that 100 million people have joined the electoral rolls since the last vote five years ago. More than half of the country is aged under 25.

Boycotted but undeterred

Modi, 20 years older than Gandhi at 63, is expected to score strongly among the young thanks to his message of aspiration and skills over the left-leaning Congress's pitch of welfare and equitable development.

But in an editorial on Monday, the Hindustan Times said that the aggressive and highly personalised campaign meant "voters were left with a lot of sound and fury but little content".

India under Modi, an unabashed nationalist, would likely result in a more muscular foreign policy at a time when the country is emerging as a defender of the developing world on issues from climate change to global trade.

But many observers worry about his domestic impact in an officially secular country.

Modi is steeped in the ideology of Hindu nationalism, which is often antagonistic towards Muslims, and he remains tainted by religious riots in Gujarat in 2002.

More than 1,000 people, mostly Muslims, died in a spasm of violence shortly after he became chief minister, leading the United States and European powers to boycott him for more than a decade.

He has never been found guilty of wrong-doing despite multiple investigations, but a woman he appointed as a minister was jailed for life in 2012 for orchestrating some of the worst of the killings.