By Subir Bhaumik
BBC News, Calcutta
Shocking pictures of a tribal woman being stripped and assaulted in India's north-eastern state of Assam have caused widespread outrage.
Hundreds of tribals were wounded in the attack
Three men arrested for the assault have been produced in court and remanded in police custody for 15 days.
Police tracked down the alleged attackers who were filmed by television cameras during Saturday's clashes between the tribals and local people.
The state government has announced a judicial inquiry into the attack.
"This is a shock to the Assamese society as a whole," Mridula Saharia, chairwoman of the Assam State Commission for Women, told the BBC. "I cannot believe this is happening in Assam."
The tribals are demanding better opportunities
Other women's groups and civil society activists in Assam have also expressed shock and called for tough action against the attackers.
The footage showed the unidentified woman being chased through the streets by three men wielding wooden clubs.
They tore off her clothes, beat her and kicked her as she tried to protect herself.
As the terrified woman ran naked through the streets, she was rescued by some local people.
Assam chief minister Tarun Gogoi has announced a judicial inquiry into Saturday's violence after the TV footage caused a furore across the country.
"I cannot see how people can become so beastly," Mr Gogoi said.
After analysing the TV footage, police arrested 18 people for Saturday's violence, including the three alleged attackers.
"The three men are in our custody and we will charge them with outraging the modesty of the tribal woman and for physical assault," Assam police chief RN Mathur said.
The three men arrested for the assault on the tribal woman include the owner of a fast-food restaurant in Guwahati.
The restaurant was among hundreds of shops damaged when tribals attending a rally in the city on Saturday ran amok, smashing cars and shops, when police refused them permission to hold a procession.
After police managed to scatter the tribal protesters, angry locals attacked them.
The tribals say at least 20 of their people were killed but the chief minister insists only two people died.
Meanwhile, a 36-hour strike called by tribal groups has paralysed life in large parts of western and northern Assam.
The "Adivasis" or tribals are descendants of those brought from central India by the British more than a century ago to work in the tea gardens of Assam as indentured labour.
They are now demanding recognition as a "Scheduled Tribe" which would bring them benefits in education and employment.