A politician in India's central state of Chhattisgarh says at least seven Congress Party workers were killed when Maoist rebels attacked his convoy.

Chhattisgarh Congress Party leader Nand Kumar Patel told reporters Wednesday that his convoy of some 20 vehicles was attacked in a roadside explosion that missed his vehicle but destroyed those behind him. Rebels opened fire on the convoy after the blast.

Patel said at least four people were injured in the attack.

While Maoist insurgents have infiltrated more than 20 Indian states, Chhattisgarh is the center of their decades-long uprising.

The rebels say they are fighting on behalf of landless farmers and tribal members disenchanted with the communist state government's attempts to push industrialization.

Indian leaders call the insurgency the country's biggest internal security threat.

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