Eight people have been arrested in the central Indian state of Madhya Pradesh over the gang-rape of three women from the Dalit lower-caste Hindu community.
Dalit women are among India's most vulnerable social groups
The attack is said to have been revenge for a Dalit boy's elopement with a girl from an upper-caste Yadav family.
A police complaint alleges that a band of about 30 Yadav men raped the boy's mother and two aunts, having first paraded them through the village.
Indian law forbids caste bias but has failed to eradicate rural prejudices.
Many Dalits - once referred to as "untouchables" - have attained positions of power but the majority are still among India's poorest, most victimised people.
Tensions boiled over in the Madhya Pradesh village of Bhamtola when a 14-year-old Yadav girl eloped with a 19-year-old Dalit boy.
At a village council meeting, the Yadavs demanded their lower-caste neighbours hand the couple over, says the BBC's Mahesh Pandey from Bhopal.
According to a police officer, the girl's brother filed a complaint and called for the marriage to be annulled.
His community members then allegedly attacked the Dalit boy's house before gang-raping three of his female relatives on Thursday night.
Security has been stepped up in the village and public gatherings banned amid fears that the incident could unleash a spiral of caste violence.