Maoist rebels killed eight Indian paramilitary troopers after detonating an explosive beneath their vehicle during a patrol in restive Chhattisgarh state, officials said Tuesday.
The blast in a remote forest region also injured three others who were airlifted to state capital Raipur for treatment, a spokesman for India's central reserve police force said.
Left-wing guerrillas have for decades been fighting the Indian state, demanding land, jobs and other rights for poor tribal groups in a long-running insurgency believed to have cost tens of thousands of lives.
Much action is focused around the rebel-dominated "Red Corridor" stretching through central and eastern India.
India's home minister Rajnath Singh described Tuesday's attack as "deeply distressing" and wished those injured a speedy recovery.
The deadly bombing followed an earlier attack by Maoist rebels on a unit of special police officers patrolling the forest.
Maoists are believed to be present in at least 20 states but are most active in Chhattisgarh, Orissa, Bihar, Jharkhand and Maharashtra.
Earlier this month at least 10 suspected rebels and one police officer were killed in a firefight deep in Chhattisgarh when hundreds of commandos staged a pre-dawn assault on a hideout.
Critics say government attempts to end the revolt through tough offensives are doomed to fail and that the real solution is better governance and development of the region.