At least 33 people have been killed and thousands left homeless in violence over the weekend between tribal people and Bangladeshi settlers in northeast India, police and hospital authorities said.

Violence between Bodo tribespeople and immigrant Muslims broke out on Friday in Rowta in Assam state's Udalguri district, about 60 miles north of Dispur, the state capital. It has since spread to neighbouring districts.

The deaths include eight people shot dead by police on yesterday. Police said they opened fire on rioters.

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Villagers from the two communities fought with guns, bows and arrows, machetes and spears. More than 100 have been injured and 50,000 have fled their homes to take refuge in makeshift camps set up by the police.

"Shoot-on-sight orders have been issued and curfew has been imposed in the violence-hit areas," Assam's chief minister Tarun Gogoi said.

Many of the dead were burned to death and more than a dozen people with serious burns have been taken to hospital in Guwahati, the state's main city.

A senior police officer, who asked not to be named, told Reuters attackers had set fire to their rivals' houses.

Authorities have called in army and paramilitary forces.

"The local administration failed to take immediate action to control the situation when the trouble initially started and later it flared up," Gogoi said.

Ringed by China, Myanmar, Bangladesh and Bhutan, India's northeast is home to more than 200 tribes and has been racked by separatist revolts since India gained independence from Britain in 1947.

Muslim settlers from Bangladesh have moved into the region in recent decades.