Mobs have destroyed more than a dozen churches and attacked Christians in eastern Orissa this week after the murder of a VHP leader in Kandhamal district, a tribal area where Christian missionaries have been active for years.

Shoot-on-sight orders and curfews to control violence have so far failed to end clashes that have killed at least 11 people.

Police deployed more than 3,000 personnel in the streets on Thursday but they could not stop the ransacking of at least one church. Local media said as many as four churches were attacked.

"Police are marching in several areas now," Orissa police chief Gopal Chandra Nanda said.

Television pictures showed mobs armed with rods putting up road blocks on Thursday and others attacking churches.

Other mobs armed with bows and arrows and axes have attacked Christian homes, dragging out women and children. Hundreds have fled to forests and nearby hills, officials said.

"Moments after we passed by a Christian village, people set it on fire and everything was over within minutes," a senior police officer, speaking on condition of anonymity, said from Kandhamal, the worst-hit district.

Around the Kandhamal area, home to around 650,000 people, more than 20 per cent of the mainly tribal inhabitants are Christian converts.

Religious violence has troubled tribal regions of Orissa for years, with Hindus and Christians fighting over conversions.

While Hindu groups accuse Christian priests of bribing poor tribes and Hindus to change their faith, the Christians say Hindus convert willingly to escape a complex caste system.

The killings have drawn international reactions. Pope Benedict has condemned the violence against Christians in Orissa but also deplored the killing of the Hindu leader.