NEW DELHI: Maoist rebels killed four policemen Wednesday in central India where the guerrillas have been waging a jungle battle for decades, an officer said.

Seven other police officers were injured in an ambush in the Narayanpur district of Chhattisgarh state, a densely forested region where security forces have been hunting the rebels known as Naxals.

District police chief Jitendra Shukla said an unknown number of Maoists opened fire on the patrol before slipping away into the jungle.

"Four of our men were killed. Seven injured have been taken to hospital in the state capital Raipur," Shukla told AFP.

Last year Maoist rebels killed 24 paramilitary policemen in the same state in an ambush on their convoy.

The guerrillas, who say they are fighting for the rights of tribal people and landless farmers, often collect funds through extortion.

The Maoists are believed to be present in at least 20 states but are most active in Chhattisgarh, Orissa, Bihar, Jharkhand and Maharashtra.

The decades-old insurgency is believed to have cost tens of thousands of lives, with much action focused around the insurgent-dominated "Red Corridor" stretching through central and eastern India.

Critics believe attempts to end the revolt through tough security offensives are doomed to fail, saying the real solution is better governance and development of the region.