The victims were clearing mines laid by rebels on a road through a densely forested area in resource-rich Chhattisgarh state when the rebels attacked from all sides.
The head of anti-Maoist operations in the state police force said one civilian was among the dead.
Maoist rebels have operated for decades across a wide swathe of central and eastern India. They have gained strength in recent times in areas where poor, tribal villagers have come into conflict with mining companies seeking resources for industrialisation.
The Maoists seek the overthrow of the Indian state, but have so far not managed to spread significantly into urban areas.
Attacks by the rebel group picked up slightly for the first time last year.
One official said: "They attack us to demoralise us, they attack us to loot our weapons."
The ambush was just a few miles from where rebels killed 27 people last year ahead of state elections.