Indian Prime Minister Narendra Modi (L) during his victory speech at the Bharatiya Janata Party (BJP) headquarters after his re-election -- the first time in almost five decades that an Indian premier has been voted back with an increased majority
Hindu nationalist Prime Minister Narendra Modi vowed to build an inclusive India on Thursday after scoring a landslide election win that he hailed as the "biggest event in world democracy".
"Together we grow. Together we prosper. Together we will build a strong and inclusive India. India wins yet again!," Modi declared amid nationwide celebrations by his right-wing Bharatiya Janata Party (BJP).
The 68-year-old leader, who built a formidable campaign based on his tough national security stance, was showered with petals when he arrived flashing "V" for victory signs at the BJP headquarters where thousands of supporters waited.
US President Donald Trump sent Twitter congratulations on the "BIG" win and added: "Great things are in store for the US-India partnership with the return of PM Modi at the helm."
Presidents Vladimir Putin of Russia, Emmanuel Macron of France and prime ministers Shinzo Abe of Japan, Scott Morrison of Australia and Benjamin Netanyahu of Israel were among world leaders to call Modi before the final results were even released, the foreign ministry said.
A rolling election commission vote count showed the BJP was on course to increase its grip on parliament with 303 out of 543 elected seats -- up from 282 in 2014.
It will be the first time in almost five decades that an Indian premier has been voted back with increased majority.
"The voting numbers in India's election is the biggest event in the history of (the) democratic world. The entire world has to recognise the democratic strength of India," Modi told cheering crowds.
The opposition Congress party was on just 52 seats, with Rahul Gandhi -- the great-grandson, grandson and son of three premiers -- conceding defeat and congratulating Modi.
The Congress tally only improved marginally from its historic low of 44 in 2014 polls.
In an added personal humiliation Gandhi, 48, also lost Amethi, a seat long held by his storied family, to a former television star running for the BJP.
The BJP headquarters in Delhi erupted in celebration with drummers, firecrackers, dancing and singing as thousands of party faithful waited in heavy rain for their leader.
"Modi will make India great again. Modi is the strongest prime minister India has ever had and will get. We need to support his policies to prosper," said one supporter, Santosh Joshi.
At Congress headquarters, a handful of dejected supporters sat in groups.
"We are sad but we will rise again. Modi won because of his lies and false promises. The country is in danger now," Rajesh Tiwari, a Congress supporter, told AFP.
India's main Sensex index breached the 40,000-point level for the first time as the count pointed to a Modi win, adding to strong gains since Monday.
- Fake news -
The vast size of India made the world's biggest election a marathon six-week endeavour.
The campaign, estimated to have cost more than $7 billion, was awash with insults -- Modi was likened to Hitler and a "gutter insect" -- as well as fake news in Facebook and WhatsApp's biggest markets.
Gandhi tried to attack Modi over a French defence deal and high unemployment and said the prime minister was dividing the officially secular country.
There has been a rise in lynchings of Muslims and low-caste Dalits for eating beef and slaughtering and trading in cattle, with critics saying extremists have been emboldened by the BJP coming to power.
- The watchman -
But Modi deftly turned the election into a referendum on his rule while depicting himself as the only one able to defend India.
He seized upon a suicide bombing, claimed by a Pakistan-based militant group, that killed 40 Indian paramilitaries in Indian-administered Kashmir on February 14. India launched a cross-border air raid and Pakistan hit back the next day.
The strikes helped Modi style himself the country's "chowkidar" ("watchman").
Pakistan Prime Minister Imran Khan on Thursday congratulated Modi and said he looked forward to working for "peace, progress and prosperity in South Asia".
Modi responded in a Twitter message thanking his arch-rival for his "good wishes" and saying he wanted peace in the region.
The messages came just hours after Pakistan said it tested a surface-to-surface ballistic missile capable of carrying conventional and nuclear warheads. India tested its latest supersonic cruise missile on Wednesday.
Analysts say Modi's victory could improve relations between the arch foes.
"The expectation in Pakistan is that there will be an incremental improvement in Pakistan-India relations as Modi's attitude would be more relaxed," retired Pakistani general Talat Masood told AFP.