Official data from the 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 Lok Sabha.
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.
His pledge to take a strong stand against the separatist movement in Muslim-majority Kashmir has also added to tensions with nuclear arch rival Pakistan.
Members of his party now want him to take a harder line on national security, as well as build a controversial temple on the site of a mosque that was demolished by a Hindu mob in Ayodhya in 1992.
“I want Modi to finish terrorism from Kashmir (and) make Pakistan bite the dust again and again,” Shekhar Chahal, a BJP worker from New Delhi said on Thursday. “I am confident that Modi will also make the temple in Ayodhya.”
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 spokesman.
“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.
Final results are due by Thursday evening.