Members of the Satra Mukti Sangram Samiti hold placards in Guwahati on Friday during a protest over sexual violence against women in the ongoing ethnic violence in Manipur. AFP

The suspects were identified from a video clip of the incident in early May that went viral on social media on Wednesday, causing outrage across the country.

"Four main accused arrested in the Viral Video Case," police in Manipur said on Twitter.

The video clip showed the women walking naked along a street, being jeered at and harassed by a mob in the state, where the authorities have imposed an Internet shutdown.

Manipur's state government, led by the ruling Hindu-nationalist Bharatiya Janata Party (BJP), said police took action when the video surfaced on social media more than two months after the incident. A "thorough investigation" was under way, the state's chief minister N. Biren Singh tweeted.

"We will ensure strict action is taken against all the perpetrators, including considering the possibility of capital punishment," he added.

The incident came at the start of the violence in Manipur, which was sparked by a dispute over access to government jobs and other perks.

Homes and churches were torched, with tens of thousands of people fleeing to government-run camps.

The clashes between vigilante gangs from rival communities have continued intermittently, pitting the majority Meitei, who are mostly Hindus and live in and around Imphal, against the mainly Christian Kuki in the surrounding hills.

In a detailed report to the court in June, civil society group Manipur Tribal Forum said many gruesome acts of violence including rape and beheading had not been investigated by state authorities.

One such incident appeared on Twitter reportedly showing an aide to a BJP lawmaker in the state holding a victim's severed head, and disappeared from the platform within hours.

The Kuki community had protested Meitei demands for reserved public job quotas and college admissions as a form of affirmative action, stoking long-held fears that they might also be allowed to acquire land in areas currently reserved for tribal groups.

Prime Minister Narendra Modi, who has faced criticism from opposition lawmakers, said on Thursday in his first public remarks on the violence that the country was "shamed" by the incident.

India's Supreme Court also warned Modi's government that, if it does not act, "we will."