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 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.