Reaching out to states complaining over NCTC, Prime Minister Manmohan Singh on Monday favoured joint and coordinated efforts to deal with challenges of terrorism whatever its origin, whether internal or external.

"There is no question that the burden of the fight against terrorism falls largely on the states' machinery. The Centre is ready to work with the states to put in place strong and effective institutional mechanisms to tackle this problem," he said.

The Prime Minister, who inaugurated the annual conference of Chief Ministers on internal security, did not dwell on the proposed National Counter Terrorism Centre, saying it will be discussed on May 5 in a separate meeting as suggested by some Chief Ministers.

Non-Congress Chief Ministers as also UPA ally Trinamool Congress chief Mamata Banerjee have raised objections to the provisions in the NCTC, contending that it will upset the federal structure and encroach on the powers of the states.

The Prime Minister warned that threats from terrorism, left wing extremism, religious fundamentalism and ethnic violence persist in the country.

"These challenges demand constant vigilance on our part.

They need to be tackled firmly but with sensitivity. The forces behind them must not only be contained but should also be effectively rolled back," he said.

"Like other internal security matters, we need joint and coordinated efforts to deal with the challenge of terrorism, whatever be its origin, whether internal or external, and whatever its motivation," Singh said.

Seeking a "holistic" approach in tackling the problem, he said, "This is a struggle in which we cannot relax. When we see turbulence in the region and growing factors of instability around us, we must strengthen our defences against terrorism."

Singh said "today, terrorist groups are nimble, more lethal than ever and increasingly networked across frontiers.

Stressing that accurate and timely intelligence was a prime necessity for defeating terrorism, Singh said some progress including strengthening intelligence gathering apparatus and establishing of NATGRID have been made.

He said the situation in some of the North-Eastern states have remained complex. "There was some improvement in terms of incidents of violence, but there is no question that much remains to be done to restore calm and eliminate extortion, kidnapping and other crimes by militant or extremist groups on the pretext of ethnic identity.

"The pilferage of development funds by militant groups is hurting our efforts to improve the lives of the people of the region. Inter-factional clashes, such as those in Tirap and Changlang, are another source of insecurity," he said.

Singh said the answers to these problems lie in strengthening the law and order capabilities of the states concerned and in reasserting and rebuilding normal democratic political and developmental processes.

"More proactive state police forces reducing reliance on central armed police forces would be a useful step forward...I would hope that the implementation of infrastructure projects in the North-East will create conditions for the return of normalcy," the PM said.

On the condition of police forces, the Prime Minister said "no system or structure can be better than the people who man it. The internal security structures of India are no exception.

"It is therefore important that we find ways and means of improving not just the number but also the quality of our police personnel," he said.