Suspected Maoist rebels have killed at least 18 villagers in the Indian state of Chhattisgarh, authorities say.

The villagers belonged to a voluntary people's movement which resists the Maoists and is backed by the state government, reports say.

Police say 15 people were wounded in the attack in Dantewada district.

Thousands have died in Maoist campaigns across central and southern India in the past 30 years. Maoists say they are fighting for the rights of the poor.

Senior district official KR Pisda told the BBC the casualties in Sunday night's incident were expected to rise.

The police said the rebels targeted local people taking part in a civil militia called Salwa Judum, supported by the state government and launched one year ago to fight the Maoists.

The rebels attacked some government-run camps for villagers and burnt down nearly 100 of them in the Arabor area, police said.

Under pressure

The government set up the camps after the authorities launched an operation against the rebels whom they accuse of killing and kidnapping villagers.

The police say more than 50,000 people live in the camps - mostly tribes people from 600 villages.

The BBC's Faisal Mohammed Ali in Delhi says the incident has raised concerns about the civil militia campaign, because of which local people have been frequently targeted by Maoists in recent months.

The militants are known as Naxalites after the district where their Maoist-inspired movement was born in the late 1960s.

They say they are fighting for the rights of indigenous people and the rural, landless poor.

They have become so powerful in some districts they run their own parallel administrations and justice systems, our correspondent says.

Nearly 6,000 people have been killed in violence linked to Maoist rebels in several southern and eastern states over the past 20 years.

The rebels are pressing for the creation of a communist state comprising tribal areas in the states of Andhra Pradesh, Maharashtra, Orissa, Bihar and Chhattisgarh.

The Indian government believes there may be 10,000 armed Maoist rebels in India, correspondents say. Nine Indian states have been affected by rebel violence.

PHOTO CAPTION

At least 25 people were killed when hundreds of suspected left-wing guerrillas attacked a relief camp in the tiny central Indian state of Chhattisgarh. (AFP)