NEW DELHI -- India's opposition leader, Narendra Modi, will become the next prime minister of the world's largest democracy, winning the most decisive election victory the country has seen in three decades and sweeping the long-dominant Congress party from power.

Modi, a career politician whose campaign promised a revival of economic growth, will have a strong mandate to govern at a time of profound changes in Indian society. Modi has said he wants to strengthen India's strategic partnership with the United States.

But critics worry the ascendance of his Hindu nationalist party could worsen sectarian tensions with India's 138 million Muslims.

The results were a crushing defeat for the Congress party, which is deeply entwined with the Nehru-Gandhi political dynasty that has been at the center of Indian politics for most of the country's post-independence history. The party, led by outgoing Prime Minister Manmohan Singh, has been plagued by corruption scandals and a poor economy.

Modi appeared before a crowd of cheering supporters Friday and tried to strike a conciliatory note.

"The era of divisive politics is over and it is time for unification," Modi, 63, said at a rally in Gujarat, where he's been chief minister since 2001. "I see the dawn of a new era for our country."

Nevertheless, Modi remains a divisive figure in the country of 1.2 billion people, in large part because he was in command in 2002 when communal rioting in Gujarat state killed more than 1,000 people -- most of them Muslims.

Modi was accused of doing little to stop the rampage, though he denies any wrongdoing and has never been charged with a crime. A Supreme Court-appointed panel found no evidence he gave orders that prevented assistance from reaching those being attacked.

He was denied a U.S. visa in 2005 for purported complicity in the riots, though as prime minister he would be virtually assured a visa.

On Friday, President Barack Obama called Modi to congratulate him on his victory and invited him "to visit Washington at a mutually agreeable time to further strengthen our bilateral relationship," the White House said in a statement. The U.S. administration had watched Modi's rise carefully, and in February an American ambassador met with him for the first time.

British Prime Minister David Cameron said on his office's official Twitter account Friday that he is "keen to work together to get the most from the U.K.-India relationship." Modi already has accepted an invitation to visit Britain, Cameron said.

By Friday night, Modi's Hindu nationalist Bharatiya Janata Party was winning enough seats in the lower house of Parliament to exceed the 272-seat majority needed to create a government without forming a coalition with smaller parties, the Election Commission said. Of the 483 seats for which results were declared, the Bharatiya Janata Party had won 271 and was leading in another 11.

The Congress party had won 42 seats and was leading in another two. Full results were expected today, but Modi's win was all but assured.

But Modi's power in Parliament won't be unchecked. While his party and its allies will have a majority in the lower house, they have only 61 of the 245 members in the upper house, where seats are distributed based on the strength of parties in state assemblies. The upper house must approve major legislation related to tax, foreign investment and constitutional changes.

There was a record turnout in the election, with 66.38 percent of India's 814 million eligible voters casting ballots during the contest, which began April 7 and was held in stages across the country. Turnout in the 2009 general election was 58.13 percent.

The last time any single party won a majority in India was in 1984, when the nation gave the Congress party a victory of more than 400 seats after the assassination of then-Prime Minister Indira Gandhi.

But 30 years later, India is in the throes of rapid urbanization and globalization just as the youth population is skyrocketing. Many new voters are far less deferential to traditional voting patterns focused on family lineage and caste. For the young Indian voters, the priorities are jobs and development, which Modi put at the forefront of his campaign.

Sreeram Chaulia, a political analyst and dean of the Jindal School of International Affairs, said the Bharatiya Janata Party's image as a purely capitalist, pro-business party resonated across India. That image contrasts with the Congress party, which is considered more of a welfare party, mixing capitalist measures with handouts for the poor.

"A lot of ordinary people believed in [Modi's] message and wanted to give him the strong mandate he was seeking, to see if he could really change things in India," Chaulia said. "There has been growth in the middle class, so of course why have they punished the incumbents? Because they want more, obviously, something more than subsistence. They want upward mobility."

The Bharatiya Janata Party has promised to change tough labor laws that make foreign manufacturers reluctant to set up factories in India. Manufacturing makes up only 15 percent of India's economy, compared with 31 percent in China. Attracting manufacturing investment is key to creating jobs for the 13 million young Indians entering the workforce each year.

But some Muslims said they were worried that their place in India could become even more tenuous, as they have fallen badly behind Hindus in recent decades in education, employment and economic status, with persistent discrimination by a Hindu majority a key reason why.

"Fear is a basic part of politics, and it's actually how politicians gain respect, but for us fear also comes from the general public," said Zahir Alam, the imam of Bari Masjid, a mosque in East Delhi. "The meaning of minority has never been clearer than it is today."

But Modi ran a campaign that focused on promises of development and good governance and largely avoided religiously divisive themes. His allies say there is no reason for Muslims to fear a national government led by him.

Indeed, candidates for the Bharatiya Janata Party won in 102 areas where Muslims make up at least one in five voters, up from just 24 of these seats in 2009, according to a Reuters analysis.

Mohammad Sabir, 25, who supplies parts for fans at a business in Varanasi, said that while he did not vote for Modi, he did not fear an administration led by him.

"He is now a national leader and he needs to focus on nation building," Sabir said. "If he cannot take everyone along, then he cannot succeed."

Although Modi focused on the economy, he has given some hints of his foreign policy leanings, saying his party wants to build on the foundations laid by Atal Bihari Vajpayee, the party's last prime minister. Vajpayee, who governed from 1998 to 2004, rode a bus across the border to Pakistan in what was seen as a bold step in trying to mend ties with India's longtime enemy.

Modi said during the campaign that India did not want a war with regional giant China but that his government would be prepared to deal with what he called Beijing's possible expansionist designs.

Modi promised a fresh start in India on Friday, noting that he is the first Indian prime minister born after independence from Britain in 1947.

"I would like to reassure the nation that while we did not get to fight and die for independence, we have the honor of living for this nation," Modi said. "Now is not the time to die for the nation but to live for it."

In sharp contrast to the street parties outside the Bharatiya Janata Party office, a sober scene played out in front of the Congress headquarters, where few showed up despite barricades erected to protect supporters from passing road traffic.

The leader of the Congress campaign, Rahul Gandhi, 43, failed to inspire public confidence. He was seen as ambivalent at best over winning a job held previously by his father, grandmother and great-grandfather.

"I wish the new government all the best," Gandhi said Friday afternoon, adding that he held himself responsible for the party's losses.

Information for this article was contributed by Muneeza Naqvi, Elizabeth A. Kennedy, Ashok Sharma and Katy Daigle of The Associated Press; by Andrew MacAskill, Unni Krishnan and staff members of Bloomberg News; and by Gardiner Harris, Max Bearak, Vivek Nemana and Betwa Sharma of The New York Times.

A Section on 05/17/2014