Government troops sent to quell communal clashes over land rights in a northeast Indian state were under orders Tuesday to shoot suspected rioters on sight after some 21 people were killed in machete attacks and dozens of homes were burned to the ground.

Some 50,000 villagers have fled to government camps for protection since violence erupted Friday between the ethnic Bodo community and Muslim settlers in Assam's western district of Kokrajhar, said the state's police chief, J.N. Choudhury.

Police have since found 21 bodies hacked with machetes and left in the jungle or by the road or riverside. Overnight, some 80 homes were burned down as the violence spread to neighbouring Dhubri and Chirang districts. No one was injured in the fires as the homes' occupants had already fled to the half-dozen or so camps set up by officials.

'We have issued shoot orders'

Some 5,000 army and paramilitary troops deployed to the region have been given a mandate to shoot suspected arsonists and rioters on sight.

Indian security personnel patrol on a street during curfew near Kokorajhar town in the northeastern Indian state of Assam on July 22. (Stringer/Reuters)

"We have decided to control the situation with a firm hand, and we have issued shoot orders," local police inspector general S.N. Singh said Tuesday.

Animosity and accusations of land-stealing have long simmered between Bodos and the thousands of mostly Bengali Muslim settlers, many of whom came from the former East Pakistan before it became Bangladesh in 1971. The two groups have clashed sporadically since 1990s and burned each other's homes and property.

A mob of more than 500 people attacked the Indian Railways showcase Rajdhani Express train Tuesday morning, pelting it with stones and bricks as it crossed the state border from West Bengal, forcing it to reverse course. Protesters among the Muslim minority staged a protest Monday that blocked the same train for five hours.

The violence has severely disrupted all regional train services, with about 30 trains delayed or cancelled, affecting some 15,000 passengers, railways spokesman S. Hajong said.

The protesters have also called a general strike to demand authorities restore order.