FILE - Naxalites, officially the Communist Party of India (Maoist) that takes its name from the Naxalbari, a village outside Calcutta where the revolt began in 1967, raise their arms during an exercise at a temporary base in the Abujh Marh forests, in the central Indian state of Chhattisgarh. AP Photo/Mustafa Quraishi, File

Bhubaneswar, India - Maoist guerrillas killed five policemen in eastern India on Monday by blowing up their vehicle, police said, in the latest of a spate of attacks that has left 13 dead since Saturday.

Maoists detonated an improvised explosive device under the vehicle close to a new police camp in a remote area of Chhattisgarh state, senior police official R.K. Vij said. The injured men were airlifted out but one died on the journey and four in hospital, he said.

Maoists killed seven police officers during an exchange of fire in another part of Chhattisgarh state on Saturday. Up to 20 rebels were killed in the battle, Vij said.

A member of India's border security force died on Sunday when rebels opened fire on a nighttime patrol, the police official said.

All the attacks took place in resource-rich Chhattisgarh, one of India's poorest regions and the site of a major security operation to flush the rebels out of their bases.

The Maoists seek the violent overthrow of the Indian state and have fought authorities for decades, particularly in rural areas of central and eastern India where they enjoy some support.

They say they are fighting to give poor farmers and landless labourers control over their land and a greater claim on mineral wealth exploited by mining companies.

The number of attacks has fallen in recent years, but security experts say the insurgency remains India's biggest internal security challenge.