India's interior minister on Thursday demanded people in a restive northeastern state surrender guns following deadly inter-ethnic fighting during which rival forces raided police stations and seized assault rifles.

Home Minister Amit Shah, speaking to reporters on a visit to Manipur's state capital Imphal, warned of "stringent charges" for those who failed to hand in their weapons before a major police sweep begins on Friday.

Shah, a key aide of Prime Minister Narendra Modi, arrived in Manipur earlier this week to tackle the unrest and also announced a probe into the causes of the violence.

Clashes erupted in May between the majority Meitei, who are mostly Hindus and live in and around Imphal, and the mainly Christian Kuki in the surrounding hills.

At least 70 people were killed and tens of thousands have fled.

Thousands of troops have been deployed to restore order.

The state's chief minister N. Biren Singh on Thursday also called for people to "surrender the arms and ammunition" they had "snatched from armed police". Security sources also confirmed to AFP that guns had been seized.

Last month, local media quoted Singh as saying that battles had involved rival groups using M16 and AK-47 assault rifles.

The far-flung states of northeast India -- sandwiched between Bangladesh, China and Myanmar -- have long been a tinderbox of tensions between different ethnic groups.

The initial spark was Kuki anger at the prospect of the Meitei being given guaranteed quotas of government jobs and other perks in a form of affirmative action.

This also stoked long-held fears among the Kuki that the Meitei might also be allowed to acquire land in areas currently reserved for them and other tribal groups.