India's parliament debated a no-confidence motion against Prime Minister Narendra Modi's government on Tuesday, a day after opposition leader Rahul Gandhi returned to the house.

The opposition Congress party launched the debate in a bid to force comment from Modi on months of deadly ethnic conflict in northeastern Manipur state, with a vote potentially to be held on Thursday.

Government minister Kiren Rijiju said the motion had "been brought at an extremely bad time and Congress would regret it later".

Modi's Hindu Nationalist Bharatiya Janata Party (BJP) won 303 seats in the 543-member lower house in the 2019 election and is expected to comfortably defeat the no-confidence vote, which it has dismissed as a headline-grabbing gimmick.

Gandhi, the scion of India's premier political dynasty, was restored to parliament on Monday after the Supreme Court last week suspended his defamation conviction over comments criticising Modi.

The 53-year-old Gandhi was sentenced to two years' imprisonment in March in a case that critics flagged as an effort to stifle political opposition in the world's largest democracy.

"This no-confidence motion is our necessity," Congress MP Gaurav Gogoi told a rowdy session of parliament.

"We had to bring it... This was never about the numbers but justice for Manipur," Gogoi said.

At least 120 people have been killed in Manipur since May in armed clashes between the predominantly Hindu Meitei majority and the mainly Christian Kuki community.

Soldiers were rushed in from other parts of India to contain the violence and a curfew and internet shutdown remain in force across most of the state.

Nishikant Dubey, a BJP lawmaker, said the Congress party's no-confidence motion was a bid to boost Gandhi's political career.

Gandhi, a lawmaker from the southern state of Kerala, has not spoken in parliament since his return. His Congress party was once a dominant force but has lost the past two elections to Modi's BJP.

He is the son, grandson and great-grandson of former prime ministers, beginning with independence leader Jawaharlal Nehru.

The weakened Congress has tried to stitch together a grand coalition with disparate regional opposition parties in the run-up to 2024 national elections, in which Modi will seek a third successive term.

Congress hopes to beat the BJP by challenging what they say is its centralised and nationalistic appeal to voters.