Indian Prime Minister Narendra Modi met allies and former mentors on Friday to plot a course for his second term after a landslide victory left the once-mighty Gandhi dynasty reeling.

A considerable to-do list includes addressing India's lacklustre economic growth and reducing unemployment, as well as fixing a stricken agriculture sector on which 70 per cent of households depend.

Modi's Hindu nationalist Bharatiya Janata Party (BJP) won 303 seats, its best ever score, giving it an even bigger majority than five years ago and defying predictions of a dip, final results confirmed on Friday.

Also read: Five challenges for India's victorious Modi

The main opposition Congress party, which has ruled the roost in India for much of its post-independence history, improved on its historic low five years ago of 44 seats but still only managed a paltry 52. Congress chief Rahul Gandhi even lost his own seat in Amethi, long a family bastion. He did win a seat in the southern state of Kerala, however, a quirk allowed under Indian election rules.

Meanwhile, Chinese President Xi Jinping joined a chorus of international well-wishers, with United States President Donald Trump hailing Modi's “BIG” win and even Pakistan's Imran Khan tweeting congratulations.

On Thursday there were delirious scenes at BJP party offices across the nation of 1.3 billion people, including its headquarters where Modi, 68, was showered with petals by chanting fans.

“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.

“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.

On Friday, ahead of a cabinet meeting, Modi conferred with two now-sidelined former mentors, LK Advani and Murli Manohar Joshi, touching their feet in sign of respect.

'Can Modi deliver?'

With the election behind him, Modi must now tackle the economy and unemployment — notably among women, who have one of the lowest labour market participation rates in the world.

“The real question is can Modi deliver on his economic commitments — for example creating the high number of jobs needed?” said Champa Patel, of the Chatham House think-tank.

“This is essential to address India's growing wealth inequalities. Can he address the challenges that millions of Indians face on a daily basis in a highly stratified country?”

India's agriculture industry is also in a dire state with drought, low prices and debt driving thousands of farmers to suicide in recent years.

The country's waterways are filthy and India is home to 22 of the world's 30 most polluted cities, killing 1.24 million people early in 2017 according to a Lancet Planetary Health study.

On Friday, around 80 to 100 people held a demonstration in Delhi as part of a global day of climate change to demand Modi does more on the environment, .

“We are here to fight for our right to breathe clean air,” said Ishika Goyal, 16.

Modi and the Hindu nationalist BJP must also try to heal divisions which have left religious minorities — including India's 170 million Muslims — feeling anxious for the future.

During the campaign he managed to deflect criticism on these issues by focusing on national security, claiming he alone could defend India.

Congress meanwhile was picking up the pieces after the second election debacle in a row, having failed to win a single seat in 13 states and five union territories.

These included Rajasthan where it won state elections late last year. This time the BJP swept all 25 seats, and in Uttar Pradesh Congress took just one constituency.

An anti-Modi alliance in Uttar Pradesh, India's most populous state with 200 million people, also failed to prevent the BJP juggernaut sweeping 64 out of 80 seats.

Even in West Bengal, run by formidable Modi critic Mamata Banerjee, the BJP made major inroads, boosting its seat tally from two to 18.

Congress on Friday was forced to deny media reports that Gandhi — the great-grandson, grandson and son of three former premiers — had offered to throw in the towel.

“The Congress leadership has clearly failed. It is a discredited and bankrupt leadership,” Kanchan Gupta from the Observer Research Foundation think-tank told AFP.

“It is astonishing that Rahul Gandhi has not yet resigned”, Ramachandra Guha, a renowned historian, said on Twitter. “The Congress should dump the Dynasty."