The Press Trust of India reported Chhattisgarh Congress leader Nand Kumar Patel and his son Dinesh, who were kidnapped by the militants during the Saturday attack, were found dead Sunday along with the bodies of eight others.
Police sources told the news agency the discovery of the bodies in the Jiram Valley in Bastar division brought the death toll to 27. Police official Ram Niwas said 32 people were injured in the attack.
Also killed in the ambush was senior Congress leader Mahendra Karma, PTI said.
Indian Prime Minister Manmohan Singh condemned what he called the "dastardly" Maoists attack on the Congress party leaders and workers in Chhattisgarh.