At least 17 people, including a six-month-old child, were killed and many wounded in fighting between indigenous tribes and Muslim settlers at the weekend in India's northeastern Assam state, police said on Monday.
Authorities imposed a night-time curfew to prevent more violence and federal troops moved into remote areas to deal with threats of more violence.
About 50,000 villagers fled their homes and took shelter in relief camps out of fear, said Donald Gilfellon, a senior civil servant in the Kokrajhar district, adding that 37 camps were set up to help the refugees and more would be opened if needed.
Sparking the clashes, unidentified men killed four youths on Friday night in the state's Bodo tribe dominated Kokrajhar district, police and district officials said. In retaliation, armed Bodos attacked Muslims, suspecting them to be behind the killings.
Ringed by China, Myanmar, Bangladesh and Bhutan, India's northeast is home to more than 200 ethnic and tribal groups and has been racked by separatist revolts since India's independence from Britain in 1947.
Strong anti-immigrant and anti-Muslim sentiment against Bangladeshi settlers has emerged among Hindu and Christian tribes in recent years.