India's ruling coalition has promised to rev up growth, double farmers' income and boost infrastructure spending in the next five years after exit polls showed it would retain power when general election votes are counted on Thursday.

Exit polls have predicted an outright majority for Prime Minister Narendra Modi's alliance in the seven-phase election that ended on Sunday. Such surveys have proved misleading before and the opposition has dismissed them as "gossip".

The coalition, the National Democratic Alliance (NDA), which is led by Modi's Bharatiya Janata Party (BJP), met in New Delhi on Tuesday confidant that victory was assured.

"The NDA has resolved to speed up economic growth and fulfil the needs of the people in the next five years of our government," Home Minister Rajnath Singh, also a senior member of the BJP, told reporters late on Tuesday.

"We're committed to a strong, developed and inclusive India."

Six of the seven exit polls conducted have predicted that the NDA would comfortably surpass the majority mark of 272 seats in the lower house of parliament.

But the main opposition Congress party has dismissed the polls and urged its workers to remain vigilant at centres where votes are being stored before the Thursday count.

Economic growth eased to a five-quarter low of 6.6% in the three months to December and there are signs it is still slowing.

March industrial output contracted for the first time in nearly two years, and surveys show a slackening in manufacturing and services growth, while car and motorbike sales have tumbled.

Some economists have called for some stimulus.

Singh said plans were ready to meet the BJP's manifesto pledge to spend Rs 100 lakh crore ($1.44 trillion) on infrastructure in the next five years and Rs 25 lakh crore on agriculture and rural development.

Singh also reiterated the BJP goal of doubling farmers' income by 2022, the 75th year of India's independence from British colonial rule.

Food Minister Ram Vilas Paswan, whose regional party is part of the NDA, said the election had unleashed a "tsunami" of support for Modi.

Political analysts say the election result could consolidate Modi's dominant position in politics while undermining the role of Congress party and opening up space for newer parties.

"If the exit polls are to be believed, Modi's image as the incorruptible defender of the faith and nation has triumphed once again," said Nikhil Menon, assistant professor of history at the University of Notre Dame.

"Narendra Modi may well be leading his party into an era of electoral dominance."

Nearly two dozen opposition parties have complained to the Election Commission of attempts to tamper with voting machines in vote-count centres. The commission has rejected the allegation.