The dead included a police constable and three special police officers (SPOs) - locals who have been recruited to act as informers and assistants for the police in their battle against the rebels.
The clash took place early on Wednesday just outside a camp housing 1,000 tribal refugees in a village of the Dantewada district of Chhattisgarh state, 480km south of the state capital, Raipur.
RK Vij, a police officer, said the Maoists tried to storm the camp but were turned back by police.
The rebels fled after reinforcements reached the area.
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Dantewada has become the epicentre of Maoist violence in India since the state government helped set up an anti-Maoist movement called Salwa Judum (Campaign for Peace) in the district last June.
About 50,000 tribespeople from 600 villages in the district have been settled in camps run by the Salwa Judum.
Human rights groups have accused the government of putting civilians in the line of fire by sponsoring the movement, and said Salwa Judum is intimidating people to join their cause.
They also accused the Maoists of killing civilians.
Chhattisgarh is the worst-hit of 13 Indian states affected by Maoist violence.
The rebels say they are fighting for millions of India's poor peasants and landless labourers.
Police said about 400 people, including 321 civilians, have been killed in the state this year.