Narendra Modi, the former teaboy who is set to become India's prime minister, swept to power promising to jolt the country from the economic doldrums but he still faces a challenge to win over suspicious religious minorities.

The 63-year-old son of low-caste parents from the western state of Gujarat will be sworn in on Monday, becoming India's 15th prime minister and the first born after independence from Britain in 1947.

The rise of one of India's most polarising public figures even split his own party, where worries about his controversial past and abrasive personality meant he had to overcome heavy internal dissent.

But since winning the strongest mandate of any Indian leader in 30 years, pro-business Modi has made efforts to sound inclusive, mend fences with rivals and promise to look after the poor.

Making his first visit to parliament last week since his victory, Modi knelt down to kiss its sandstone steps, calling the building a "temple of democracy".

He also choked back tears as he promised to serve India as his "mother" -- declaring his government would work to lift up the common man as well as "the weak and the pained."

A yoga-lover and strict vegetarian, Modi was long seen as a hardliner within the right-wing Bharatiya Janata Party (BJP), steeped in the ideology of Hindu nationalism, having joined the Rashtriya Swayamsevak Sangh as a boy.

Committed to defending Hindu culture, the RSS has been banned twice since independence and its cadres often harbour hostile views of India's 150 million Muslims, the country's largest religious minority.

While Modi successfully campaigned on a platform of good governance and economic revival, his links to anti-Muslim violence in Gujarat in 2002, in which more than 1,000 people died, mean he is still viewed with suspicion by some.

He was chief minister when the savage riots broke out and, although he has never been found guilty of wrongdoing, the failure of his administration to confront the violence left a legacy of distrust and suspicion.

His refusal to apologise and his decision to appoint a woman to his cabinet who was later found guilty of orchestrating some of the worst of the killing added to the rancour.

The United States and European powers boycotted him for more than a decade.

- Non-Westernised -

From one of India's "backward castes", Modi grew up in a dusty village in Gujarat where electricity was scarce and his father's tea-stall earnings bought few luxuries.

Unlike many of India's former leaders, he has no foreign education, having left school at 17 and gained his degrees through distance learning.

He is far more comfortable speaking Hindi or his native Gujarati than English, while his foreign travels have taken him more frequently to East Asia than the West.

"Modi is a Gujarat-born Indian, who is not too comfortable with Western modes of living nor is he Western in his mannerisms," said Rudrangshu Mukherjee, an Indian historian.

"And he is not ashamed of it."

The Guardian newspaper said last week in an editorial that Modi's victory represented the day "when Britain finally left India", underlining how little the former colonial power had shaped the new prime minister.

He won support from across India in urban and rural areas and particularly among the young who were attracted to his record as a business-friendly administrator during his 13 years running Gujarat as chief minister.

His over-arching message was simple and aspirational: India needs development and corruption-free government to eradicate its poverty and provide jobs to its teeming population.

But critics note a lack of progress on human development indicators during Modi's rule in Gujarat, saying his cosy relationship with industrialists amounts to crony capitalism.

The state also failed to appoint an anti-corruption ombudsman for nearly a decade until 2013, and one of his closest aides, Amit Shah, faces murder and extortion charges dating to his time as home minister.

His "strong" leadership is a result of his ruthless centralisation of power which tips into authoritarianism whenever he is challenged, they say.

Modi lives alone and is known to confide in a small circle of trusted aides.

He walked out of a child marriage arranged by his parents and only acknowledged reports he was still wed in his election nomination papers.

Biographers say as a young adult, he wandered into the Himalayas on a spiritual discovery journey, returning to plunge into Hindu nationalist politics in which he earned an early reputation as a formidable organiser.