India begins voting Friday in a six-week election, with Hindu nationalist Prime Minister Narendra Modi's victory all but assured, raising concerns for the health of the world's largest democracy.

Modi remains roundly popular after a decade in office that has seen India rise in diplomatic clout and economic power, as well as efforts by his government to bring the country's majority faith in ever closer alignment with its politics.

Analysts have long expected him to win against a fractious alliance of more than two dozen parties who have yet to name a candidate for prime minister.

Modi's prospects have been further bolstered by several criminal probes into his opponents, sparking concerns from UN rights chief Volker Turk and human rights organisations that the vote will be skewed.

"I don't need the United Nations to tell me our elections should be free and fair," foreign minister S. Jaishankar told reporters while campaigning this month.

"The people of India will ensure that," he added. "So don't worry about it."

Modi, 73, has already led the ruling Bharatiya Janata Party (BJP) through two landslide victories in 2014 and 2019, forged in part by his appeals to the Hindu faithful.

This year in the town of Ayodhya, he presided over the inauguration of a grand temple to the deity Ram, built on the grounds of a centuries-old mosque razed by Hindu zealots.

Construction of the temple fulfilled a long-standing demand of Hindu activists and was widely celebrated across India with back-to-back television coverage and street parties.

"The nation is creating the genesis of a new history," he told the thousands gathered for the ceremony, among them Bollywood celebrities and cricket stars.

- 'Our ability to fight' -

The opposition Congress party, which ruled the country almost uninterrupted for decades after independence from Britain, is meanwhile a shadow of its former self and out of office in all but three of the country's 28 states.

Its leaders have stitched together an alliance of more than two dozen regional parties to present a united front against the BJP's well-oiled and well-funded electoral juggernaut.

But the bloc has been plagued by disputes over seat-sharing deals and suffered the defection of a leading member to the government.

It has also accused Modi's government of using law enforcement agencies to selectively target the bloc's leaders, several of whom are the subject of active criminal investigations.

Among them is Delhi chief minister Arvind Kejriwal, who was arrested last month and remains in custody on allegations his party received kickbacks while handing out liquor licences to private companies.

Rahul Gandhi is the most prominent Congress politician, and his father, grandmother and great-grandfather all served as prime minister.

He was briefly disqualified from parliament last year after being convicted of criminal libel.

His party's bank accounts have been frozen since February by India's income tax department after a dispute over returns that were filed five years ago.

"We have no money to campaign, we cannot support our candidates," the 53-year-old told reporters last month. "Our ability to fight elections has been damaged."

- 'Contempt for all dissent' -

Modi's tenure has seen India overtake former colonial ruler Britain as the world's fifth-biggest economy, with Western nations lining up to court a prospective ally against regional rival China's growing assertiveness.

In doing so, they have sidestepped concerns over the taming of India's once-vibrant press and restrictions on civil society that have seen rights groups like Amnesty severely curtail their local operations.

Last year, the tax office raided the BBC's local offices weeks after the British broadcaster aired a documentary questioning Modi's role in 2002 religious riots that killed around 1,000 people, most of them Muslims.

Should Modi win again, his third term "will be even more characterised by contempt for all dissent", political scientist Suhas Palshikar told AFP.

Gandhi has criticised the government for democratic backsliding and its chest-thumping Hindu nationalism, which have left many among the country's 220-million-strong Muslim minority fearful for their futures.

But Gandhi has already led Congress to two defeats against Modi and his efforts to dent the premier's popularity have failed to register with voters.

Published opinion polls are rare in India, but a Pew survey last year found Modi was viewed favourably by nearly 80 percent of the public.

A total of 968 million people are eligible to vote in the election -- more than the entire population of the United States, European Union and Russia combined.

Voting will be staggered over seven stages between April 19 and June 1, with more than a million polling stations across the country.

Ballots from around the country will be counted all at once on June 4 and are usually announced on the same day.

Modi: tea seller's son who became India's populist hero

Once shunned and now eagerly courted by the West, Prime Minister Narendra Modi has steered India away from its secular traditions and towards the muscular Hindu-first politics he championed for decades.

Modi's political ascent was marred by allegations of his culpability in India's worst religious riots this century, and his tenure has dovetailed with rising hostility towards Muslims and other minorities.

He is also consistently ranked among the world's most popular leaders, and is roundly expected to coast to a third term after a marathon national election starting Friday.

Supporters revere his tough-guy persona, burnished by his image as a steward of India's majority faith and myth-making that played up his modest roots.

"They dislike me because of my humble origins," he said in rallies ahead of the last elections, lambasting his opponents.

"Yes, a person belonging to a poor family has become prime minister. They do not fail to hide their contempt for this fact."

Modi was born in 1950 in the western state of Gujarat, the third of six children whose father worked as a tea vendor at a railway station.

An average student, his gift for rousing oratory was first seen with his keen membership of a school debate club and participation in theatrical performances.

But the seeds of his political destiny were sown at the age of eight when he joined the Rashtriya Swayamsevak Sangh (RSS), a hardline nationalist group.

Modi dedicated himself to its cause of promoting Hindu supremacy in nominally secular India, even walking out of his arranged marriage soon after his wedding aged 18.

Remaining with his wife -- whom he never officially divorced -- would have hampered his advancement through the ranks of the RSS, which expected senior cadres to stay celibate.

- Deadly riots -

The RSS groomed Modi for a career in its political wing, the Bharatiya Janata Party (BJP), which through the 1990s was growing into a major force.

He was appointed chief minister of Gujarat in 2001 but the following year the state was rocked by sectarian riots, sparked by a fire that killed dozens of Hindu pilgrims.

At least 1,000 people were killed in the ensuing violence, with most of the victims minority Muslims. Modi was accused of both helping stir up the unrest and failing to order a police intervention.

Modi later told a BBC reporter that his main weakness in responding to the riots was not knowing "how to handle the media".

A probe by India's top court eventually said there was no evidence to prosecute Modi but the international fallout saw him banned from entering the United States and Britain for years.

But it was a testament to India's changing political tides that his popularity only grew at home.

He built a reputation as a leader ready to assert the interests of India's majority faith, which he contended had been held back by the secularist forces that ruled the country almost continuously since independence from Britain.

- 'A new history' -

The BJP has won two thumping election victories with Modi at the helm, and a decade after becoming prime minister in 2014 he looks unassailable against a firmly loyal party machine and a hapless, divided opposition.

Critics have sounded the alarm over a spate of prosecutions directed at Modi's political rivals and the taming of a once-vibrant press.

India's 210-million-strong Muslim community is also increasingly anxious about its future -- Modi's rise to the premiership was followed by a spate of lynchings targeting Muslims for the slaughter of cows, a sacred animal in the Hindu tradition.

But Western democracies have sidestepped rights concerns in the hopes of cultivating a regional ally that can help check China's growing assertiveness.

Modi was last year accorded the rare honour of a joint address to the US Congress and a White House state reception at President Joe Biden's invitation.

He has taken credit for India's rising diplomatic and economic clout, claiming that under his watch the country has become a "vishwaguru" or teacher to the world.

Only now is India assuming its rightful global status, his party contends, after the historical subjugation of the country and its majority faith -- first by the Islamic Mughal empire and then by the British colonial project.

Modi's government has refashioned colonial-era urban landscapes in New Delhi, rewritten textbooks and overhauled British-era criminal laws in an effort to erase what it regards as symbols of foreign domination.

This project reached its zenith in January when Modi presided over the opening of a new temple in the town of Ayodhya, built on grounds once home to a centuries-old Mughal mosque razed by Hindu zealots in 1992.

Modi said during the elaborate ceremony that the temple's consecration showed India was "rising above the mentality of slavery".

He added: "The nation is creating the genesis of a new history."

All you need to know

Voting in India's six-week election begins Friday, with 968 million people eligible to cast their ballots in the world's biggest democratic vote.

AFP explains how the poll is conducted and what is likely to happen:

- How do people vote? -

All Indian citizens aged 18 and above are eligible to vote -- that's 968 million people, according to the election commission.

Turnout during the last national elections was more than 67 percent, with nearly 615 million people casting a ballot.

India uses electronic voting machines that allow for faster counting of ballots.

The election commission says there is no way to connect to the machines remotely and no way to compromise the results.

Election officials travel by foot, road, trains, helicopters, boats, and occasionally camels and elephants to set up polling stations in remote locations.

They are sometimes accompanied by security forces in areas with a history of insurgent violence.

- Why will it take so long? -

The sheer number of voters means that every time India holds a national election, it marks the largest exercise of the democratic franchise in human history.

A total of 15 million people will work the polls, including people temporarily assigned from elsewhere in the civil service.

Complicating the challenge are electoral laws requiring that each voter is no more than two kilometres (1.2 miles) away from a polling booth.

During the last election in 2019, for example, a polling booth was set up for a single voter living deep inside a forest in the western state of Gujarat.

Organisers say it is impossible to operate the 1.05 million polling stations needed around the country on a single day.

To ease the immense logistical burden, voting is staggered over six weeks starting from April 19.

Local weather, religious festivals, farm harvests and school terms are also taken into account to make sure voters in each corner of India can go to the polls at the most convenient date.

- How much does it cost? -

Election and campaign spending have grown in tandem with India's booming economy, now the fifth-largest in the world after overtaking former colonial master Britain in 2022.

An estimated $8.7 billion was spent by organisers, political parties and candidates in 2019, according to a report by the Centre for Media Studies (CMS).

Around a quarter of that figure came in the form of cash payments made directly to voters by candidates in an attempt to sway their decision, the report said.

The same think tank told Indian media in February that it forecast spending to exceed $14.2 billion for this year's contest.

That figure is almost on par with political spending in the United States for the 2020 congressional and presidential elections.

- What will happen? -

Prime Minister Narendra Modi is seeking a third consecutive term, and nearly all observers agree his chest-thumping appeals to Hindu nationalist sentiment will again prove an election winner.

Modi, 73, remains robustly popular after a decade in power, with a Pew survey last year finding he was viewed favourably by nearly 80 percent of Indians.

His opponents have been hamstrung by infighting and what they say are politically motivated criminal cases aimed at hobbling challengers to Modi's ruling Bharatiya Janata Party (BJP).

Speculation has focused not on whether the BJP will win but on the magnitude of its victory, with party figures publicly confident they will secure a two-thirds majority in the lower house.

Such a result would give it a freer hand to make changes to India's nominally secular constitution and pursue other long-held ideological passion projects.

That could include a new civil code to standardise the patchwork of marriage and divorce laws that apply to Muslims, Sikhs and other minorities, a deeply contentious move opposed by those communities.

- When will we know who won? -

Publication of exit poll data while an election is in progress is illegal under Indian law, so any indication of which way the vote is trending will only come after the last phase of voting concludes on June 1.

Formal ballot counting begins three days later on June 4, though the use of electronic voting machines means tallying will be quick. Results should be announced the same day.

The party with a simple majority of 273 or more seats in the lower house is invited to form a government with its choice of prime minister.

If no single party reaches that mark, India's president will ask the leading party to try to put together a coalition.

In past decades, that has led to days, and sometimes weeks, of intense horse-trading and negotiations between parties to cobble together a working majority.