Armed group attack convoy carrying paramilitary forces, confiscate weapons and radio sets, officials say.
Suspected Maoist rebels have killed 11 paramilitary commandos on Saturday in a remote part of central India after ambushing their convoy, police said, the latest attack in a simmering internal conflict.
The troops were on their way to provide protection to workers for a road construction project when the gunmen attacked, a senior police officer of the restive Chhattisgarh state said.
The assault is the latest in a deadly conflict that pits the fighters against local and national authorities in the forests and rural areas of mainly central and eastern India.
The armed group, who say they are fighting for the rights of tribal people and landless farmers, often collect funds through extortion.
"We can confirm that 11 security personnel have lost their lives in the ambush which was carried out by Maoist rebels in Sukma district," police deputy inspector general Sundarraj P told AFP news agency.
"Three other CRPF (Central Reserve Police Force) personnel are critically injured. We have deployed helicopters to evacuate them."
The rebels also snatched weapons and radio sets from the attack site, local media reports said.
The Maoists are believed to be present in at least 20 states, but are most active in Chhattisgarh, Orissa, Bihar, Jharkhand and Maharashtra, occupying thousands of square kilometres of land.
The decades-long conflict is believed to have cost tens of thousands of lives, with much action focused around the so-called "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 development of the region.