New Delhi - Twelve paramilitary troopers were killed and 11 injured when their vehicle hit a landmine planted by Maoist rebels in the central Indian state of Chhattisgarh, news reports said Sunday.

The troopers were killed Saturday evening in a forested area of Tongapal in Dantewada district, about 500 kilometres south of the state capital Raipur, IANS and PTI news agencies reported.

A 40-member squad of the Central Reserve Police Force and district police was returning to base camp after searching for Maoist rebels, police said.

The victims were travelling in a truck which hit the landmine. Seven men died on the spot and four on their way to hospital, TJ Longkumer, inspector general of police, said.

"One more succumbed to injuries midnight at the hospital where 11 men were rushed in a critical condition," Longkumer added.

He said the toll could go up as some policemen were still missing.

"We have rushed extra police forces to the attack site," Longkumer said.

The police team was returning from a village in the Tongepal area after receiving information that the Maoist rebels had set fire to some trucks used in road construction.

An unnamed local police official was quoted as saying rebels burned the trucks to lure the soldiers into an ambush in Bastar area of the Dantewada forests.

Chhattisgarh police estimate that roughly 10,000 rebels operate in the southern part of the state that includes Dantewada and Bijapur districts.

Maoists guerrillas operate in 13 of India's 29 states. The Bastar region, which has a large tribal population and poor development, is one of their strongholds, authorities say.

The rebels recently declared an area of eastern West Bengal state a "liberated zone" following which the state sent in police and paramilitary forces.

Prime Minister Manmohan Singh has described the Maoist insurgency as one of the gravest internal security threats facing India.(dpa)