Opposition candidate Narendra Modi will be the next prime minister of India, with counting trends showing the pro-business Hindu nationalist and his party headed for the most resounding election victory the country has seen in 30 years.

Modi's landslide win was welcomed with a thundering rally on India's stock markets and raucous celebrations at offices across the country of his Bharatiya Janata Party (BJP), where supporters danced, exploded fireworks and handed out sweets.

Prime Minister Manmohan Singh, whose Congress party headed for a crushing defeat, telephoned Modi to congratulate him on his success, the prime minister's office said.

Crowds surged around Modi's car after he visited his mother's home in the western state of Gujarat. He sent a message saying "India has won," that instantly set a record as the country's most retweeted Twitter post.

"I'm so happy because all of India wanted a strong government," said software engineer Vinod Rai as he embraced friends and shouted in joy at the BJP's Delhi headquarters, his forehead smeered with vermillion red.

The party was headed for a majority in parliament, giving Modi the most decisive mandate for any leader since the 1984 assassination of prime minister Indira Gandhi propelled her son to office. Since 1989, India has been governed by coalitions.

The BJP was winning in 277 seats of the 543-seat parliament, counting trends showed. An alliance led by the party was ahead in 336 seats, TV channel NDTV said.

Responding to the news Indian markets got off to a roaring start, with the rupee breaking below 59 to the U.S. dollar, an 11-month high, and the benchmark stock index jumped 6 percent before paring its gains.

Betting on a Modi win, foreign investors have poured more than $16 billion into Indian stocks and bonds in the past six months and now hold over 22 percent of Mumbai-listed equities - a stake estimated by Morgan Stanley at almost $280 billion.

Unlike his predecessors, Modi will not have to deal with unruly partners as he implements reform. That could usher in profound economic changes, and he will try to replicate his success in attracting investment and building infrastructure in Gujarat, the state he has governed for 12 years.

"He can afford to have a smaller but stronger cabinet, that means a far more decisive government. He has been saying less government and more governance, we are really likely to see that," said Navneet Munot, Chief Investment Officer at SBI Funds management in Mumbai.

But with India's economy suffering its worst slowdown since the 1980s and battling high inflation, it will not be an easy task to meet the hopes of millions of Indians who have bought into the idea that Modi will quickly push their country onto the top table of global economic powers.

"People will not give him much time to deliver," said Neerja Chowdhury, a political analyst and a former political editor of the Indian Express newspaper. "On the economic reform agenda, I think he will move very quickly ... he's a doer and he's very focused."

DESIRE FOR CHANGE

The 63-year-old's promises of job creation and clean, efficient government resonated with many of the half a billion people who braved blistering summer heat to vote in the world's biggest election over the last five weeks.

Since being named as his party's candidate last September, Modi has flown 300,000 km and addressed 457 rallies in a slick, presidential-style campaign that has broken the mould of Indian politics.

Modi's media-savvy, modern campaign ran circles round his slow-footed rival, Rahul Gandhi, 43, from the Congress party. The Congress, which led India to independence from Britain, was headed for its worst-ever result after two terms in office marred by corruption and a floundering economy.

Prime Minister Singh, who as finance minister launched reforms in 1991 that brought an end to decades of economic isolation, has already bid farewell to his staff after ten years in office marked by mounting policy paralysis.

The desire for change has been so strong that voters put aside concerns about Modi's Hindu-centric politics. A dark chapter of violence against Muslims on his watch has mattered less and less to many, including a bulging middle class alarmed by dwindling purchasing power and job opportunities as the economy slumped to sub-five percent growth in the last two years.

Gandhi was leading by a slender margin in his seat of Amethi, a family bastion that has been held in turn by his uncle, father and mother, Sonia. A loss there would spell disaster for the great grandson of India's independence leader.

Modi has promised that, if elected, he would take decisive action to unblock stalled investments in power, road and rail projects to revive economic growth.

Tax and labour market reforms, backed by a gradual opening up to foreign investment, would seek to create the 10 million jobs that Asia's third-largest economy must create every year to employ young people entering the workforce.

Modi watched the results on TV at his home in Gujarat then met his mother, 95-year-old Hiraben, at his brother's modest government flat in the state capital, Gandhinagar. He touched her feet and she put a red stripe on his forehead as a blessing, while crackers burst outside amid chants of "Modi, Modi."

He was later expected to embark on a victory tour to his local constituency of Vadodara, while party workers in New Delhi hoped he would go to there later for what could be a hero's welcome. - Reuters