Police in India have stepped up security across India but especially in trouble hotspots Orissa and Karnataka to ensure a peaceful Christmas for Christians.

In Bangalore, Karnataka, which recently witnessed a series of attacks on churches and a number of accusations against Christians of forced conversions, Christians have been advised to keep Christmas celebrations low key and churches have installed CCTV cameras.

Fr Foustine Lobo, of the Archdiocese of Bangalore, told the Times of India on Sunday that special security measures were in place for the holiday week.

"We've hired security guards and will also be in touch with the police," he said.

Police commissioner Shankar Bidari said Christians were free to mark the festival without hindrance.

"Devotees may observe mass in their respective churches or indoors without permission," he said. "There won't be any restrictions on time."

Churches have been asked to contact police if they feel threatened.

In Kolkata, Bishop Ashok Biswas said police have met church leaders to discuss precautionary measures.

"Respective churches have been asked by us to take necessary measures to ensure that everything goes smoothly. Police have surveyed the premises and gathered information. I am sure they will take measures to ensure security for those attending mass," he added.

"We shall not restrict entry, but take special precautions to ensure that nothing goes wrong. We have contacted the local police station and there will be two rounds of screening before people are allowed in," said the Rev Arghya Biswas of St Paul's Cathedral.

In Orissa, dozens of Christians were killed and tens of thousands were displaced in violence triggered in August by the death of a radical Hindu leader. The government has deployed more paramilitary forces to the region where Christians remain tense even after a nationalist group called off its planned 'bandh', or shutdown.

"We have kept a close watch on roads, outside churches and increased night patrolling ensuring that no expense is spared for a peaceful Christmas," said Deputy Inspector General (Southern Police Range) RP Koche.

The Times of India reported that 4,000 policemen and security personnel had been deployed to Orissa state.