Violence is spreading in northeast Assam state after nine more people were killed in overnight clashes between ethnic groups in India's northeast, bringing the death toll to 36 with about 170,000 villagers displaced by the unrest, officials say.
"The situation is tense and we are getting additional paramilitary troopers," Assam police chief JN Choudhury told reporters on Wednesday.
Rioting between Bodo tribespeople and Muslim settlers has raged for days in a region near Bangladesh.
Indian security forces patrolled deserted streets on Wednesday, and were given orders to shoot on sight, officials said.
Hagrama Mohilary, chief of the Bodoland Territorial Council, a local government body, told the AFP news agency that "an estimated 170,000 are sheltered in government-run relief camps".
A curfew is in place and government troops have been deployed in the area, Al Jazeera's Prerna Suri reported from Assam's capital Guwahati.
Ringed by China, Myanmar, Bangladesh and Bhutan, India's northeast is home to more than 200 ethnic and tribal groups and has been wrecked by separatist revolts since India's independence from Britain in 1947.
Muslim Bangladeshis make up most of the illegal immigrants.
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 youth 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.
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 Guwahati to New Delhi.
An official 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 have been closed in areas affected by the unrest and soldiers and federal paramilitary forces have been patrolling remote districts.