Police say Maoist rebels have killed five policeman in the central Indian state of Chhattisgarh.

The five officers died in a shootout with rebels who attacked a police camp in the Naryanpur district early Thursday. There were no reports of casualties among the attackers.

Late last month, Maoist rebels ambushed a group of police investigating Maoist activity in the Sunabeda reserve along the border of Orissa and Chhattisgarh states. Nine policemen were killed in the attack.

Earlier in May, seven policemen died in a landmine attack by Maoist rebels in Chhattisgarh.

Indian leaders call the 40-year Maoist insurgency the country's biggest internal security threat.

The rebels have infiltrated more than 20 Indian states, saying they are fighting for jobs and land for the poor.

Indian officials say close to 1,200 people were killed in rebel-related violence in 2010. More than 250 people have been killed so far this year.