Indian Prime Minister Narendra Modi claimed victory Thursday in India's general election and vowed an "inclusive" future, with his party headed for a landslide win. 

BJP supporters celebrate after learning the initial election results outside the party headquarters in New Delhi, India, May 23, 2019. (Photo: VCG)

With around half the 600 million votes cast counted, Election Commission data showed Modi's Bharatiya Janata Party (BJP) winning 300 of India's 543 elected lower house seats.

 "Together we grow. Together we prosper. Together we will build a strong and inclusive India. India wins yet again!" Modi tweeted as the outcome of the world's biggest election became clear.

The preliminary count predicts a commanding majority in the lower house for the BJP and its allies, who are on course for almost 50 additional seats.

They will still lack a majority in the upper house, however, putting a brake on Modi's legislative agenda.

"Today's mandate... shows that people of India have entirely uprooted casteism, nepotism and appeasement to choose nationalism and development," tweeted BJP president Amit Shah, in a swipe at Congress and Gandhi.

Celebrations broke out at BJP offices including in Mumbai where a few hundred party supporters and workers danced, played drums, chanted slogans and waved party flags.

India's main Sensex index breached the 40,000-point level for the first time as the count pointed to a Modi win, following strong gains since Monday.

"Time for transformation of India. Time for deep reform. I dream of us as a global superpower in my lifetime," tweeted India's richest banker, Uday Kotak, as he congratulated Modi.