Prime Minister Manmohan Singh on Sunday said that the response to the left-wing extremism must be "calibrated" to avoid alienation of people, especially those in tribal areas.

The prime minister, who was speaking at the Chief Ministers' Conference on Internal Security in New Delhi, said the anti-Naxal operations should go hand-in-hand with social and economic development.

"Our response to left-wing extremism must be calibrated to avoid alienating our people, especially those in tribal areas," he said.

"It must also go hand-in-hand with social and economic development of areas affected by left-wing extremism, bringing them into the mainstream of national progress," Singh said.

The prime minister, who reaffirmed his earlier stand that Naxalism is the greatest threat to internal security, said, "Tribal communities should get full benefit of our schemes and programmes. This is only possible by improving service delivery in tribal-dominated areas."

The anti-Naxal operation started by the Home Ministry in close coordination with various states will see over 60,000 central security personnel in action besides the state police forces.