Thousands of people have fled their homes in India's northeastern Assam state after fighting between indigenous tribes and Muslim settlers killed at least 30 people, wounded many more, and left villages in flames, police said.
Security forces fired warning shots to disperse armed groups that were moving between jungle hamlets on Monday, setting fire to bamboo houses, police and aid workers in the area told the Reuters news agency.
Soldiers and federal paramilitary forces were patrolling remote districts.
"We saw miscreants burning down village after village on Monday," a senior police officer who asked not to be identified said.
"It's total madness going on here. People have lost their senses".
SN Singh, Assam's inspector general of police, told Reuters he had ordered his men to shoot at gangs on the streets on sight after a dawn-to-dusk curfew was imposed to stop the violence spreading.
Ringed by China, Myanmar, Bangladesh and Bhutan, India's northeast is home to more than 200 ethnic and tribal groups and has been wracked by separatist revolts since India's independence from Britain in 1947.
In recent years, Hindu and Christian tribes have begun to give vent to strong anti-immigrant and anti-Muslim sentiment against Bangladeshi settlers.
The latest wave of violence was sparked on Friday night when unidentified men killed four youths in the state's Bodo tribe-dominated Kokrajhar district near the borders of Bangladesh and Bhutan, police and district officials said.
In retaliation, armed Bodos attacked Muslims, suspecting them to be behind the killings.
About 50,000 villagers have fled their homes and taken shelter in relief camps out of fear since then, said Donald Gilfellon, a senior civil servant in the Kokrajhar district, adding that 37 camps had been set up to help the refugees and that more would be opened if needed.
"Schools and government buildings are getting over-crowded. More and more people are coming, we have given up counting," another district civil servant, who requested not to be named, said.
Police said unidentified groups had fired indiscriminately with automatic weapons in populated areas over the weekend.
On Sunday, the body of a six-month-old child was found by villagers on a river bank along with the body of a woman, police said.
On Monday afternoon, hundreds of people carrying spears squatted on the railway line linking Assam's capital Guwahati to New Delhi.
Singh said they had stopped an express train for several hours, demanding that the authorities release several men detained in connection with the killings of the four youth.
Businesses, offices and schools remained closed on Monday, and streets were deserted in Kokrajhar town as heavily armed security men patrolled on foot and in mine-proof vehicles.
"We can't think of going back home. Our village is vulnerable to attacks and the government failed to give us
protection," resident Hiranya Musaharay said by phone from Kokrajhar town where he was staying with relatives.