The targeted group were returning from a road-opening ceremony when they were attacked by a large number of heavily armed militants, the head of anti-Maoist operations in the state, Ram Niwas, said by telephone.
Other local police sources said the Maoists, who massacred 76 policemen in Chhattisgarh in April, might have numbered as many as 100.
The officers were surrounded in the ambush, which took place in Dhodai, 300 kilometres (190 miles) south of Chhattisgarh state capital Raipur, and they fought back in a gunbattle that lasted three hours, the police said.
Some of injured were evacuated by helicopter, and reinforcements were sent to the area.
The government launched a major offensive last year to tackle the worsening left-wing insurgency, but since then the Maoists have hit back with a series of bloody strikes.
Maoist rebel groups have fought for decades throughout east India against state and central government rule, drawing support from landless tribal groups and farmers left behind by the country’s economic expansion.