Indian supporters and party workers of the Bharatiya Janata Party wear masks of Indian Prime Minister Narendra Modi and flash victory signs as they celebrate the results of India’s general election, in Bangalore on Thursday. Photo: AFP

 
Indian Prime Minister Narendra Modi promised to unite the country on Thursday after a huge election win, with his party on course to increase its majority on a mandate of pursuing business-friendly policies and a hard line on national security.

Official data from India's Election Commission showed Modi's Hindu-nationalist Bharatiya Janata Party (BJP) ahead in 298 of the 542 seats available, up from the 282 it won in 2014 and more than the 272 seats needed for a majority in the lower house of parliament.

That would give it the first back-to-back majority for a single party since 1984.

"Together we will build a strong and inclusive India," Modi said on Twitter on Thursday. "India wins yet again!"

Modi's victory boosted financial markets as investors expect his government will continue to pursue economic reforms. He will be under pressure to create employment for the tens of millions of young people coming on to the jobs market in the next few years and to boost depressed farm incomes.

"The immediate challenges are to address employment, the issue of agricultural income and revive the banking sector," said Madan Sabnavis, chief economist at Care Ratings in Mumbai.

But making good on his promise to unite the country will be difficult as the BJP campaign was often divisive, prompting the minority Muslim community to express fears that they were being treated as second-class citizens.

Pakistani Prime Minister Imran Khan on  Thursday congratulated Modi and his party on their election victory, saying he looked forward to working with Modi for "peace, progress and prosperity in South Asia."

"Congratulate Prime Minister Modi on the electoral victory of BJP and allies. Look forward to working with him for peace, progress and prosperity in South Asia," Khan tweeted.

At BJP headquarters in New Delhi, party workers set off firecrackers and began decorating the building with floral decorations ahead of an expected victory party.

"It's a stamp of approval by voters on the honest and decisive leadership of Prime Minister Modi," said Nalin S Kohli, a BJP spokesman.

Congress leaders were sombre.

"Why despite a weak economy people preferred the BJP is something we have to understand," said Salman Soz, a party spokesperson.

"People have given them a second chance. I hope they use it well."

The NDA's predicted margin of victory, at 348 seats to 85 for the Congress-led United Progressive Alliance, according to TV channel NDTV, is much larger than surveys indicated in the run-up to the vote, when most polls showed it would be the largest alliance but would fall short of an overall majority.

The BJP has also capitalized on the star power of Modi, a frenetic campaigner, as well as superior financial resources.

It outspent Congress by six times on Facebook and Google advertising, data showed, and by as much as 20 times overall, sources told Reuters this month.