India's Prime Minister Manmohan Singh said Monday that Maoist rebels continue to pose one of the biggest threats to the country's internal security.

Hosting an annual conference in New Delhi of chief ministers from most of India's states, Mr. Singh said the Maoist insurgency now affects nine states.

“Threats from terrorism, left-wing extremism, religious fundamentalism and ethnic violence persists in our country. These challenges demand constant vigilance on our part. They need to be tackled firmly, but with sensitivity. It is an endeavor that requires the united effort of us all, both at the center and in the states.”

The rebels say they are fighting for the rights of the poor and landless against what they say are severe inequities in land acquisition and natural wealth distribution.

The government in New Delhi is facing heavy criticism from state governments and even political allies over plans to create a National Counterterrorism Center. Some chief ministers say the center will disturb the federal-state balance of power.

But Prime Minister Singh said the central government is an ally of states on internal security issues, not an opponent.

Indian Home Minister P. Chidambaram warned that insurgents are becoming better armed and more sophisticated, and must be combated on a national scale. But the chief minister of western Gujarat state accused the government of acting “unilaterally” and not consulting states sufficiently on security issues.

The government in New Delhi is scheduled to hold a separate meeting with chief ministers on the proposed counterterrorism center next month.