At least six policemen including a senior officer were killed after Maoist rebels ambushed a police party in Central Indian state of Chhattisgarh, Police said Friday. Police said the incident happened in Kuakonda area of Shamgiri Hills in Dantewada district of Chattisgarh, adding, a contingent of ten policemen was on a search patrol when Maoists rebels attacked them with automatic rifles leaving seven policemen dead. The police said the seven dead include two members of paramilitary officials, including a deputy commandant. Police said additional reinforcement of troops has been send to the spot to catch the rebels. Senior security and administrative officials have also reached the spot to take stock of the situation, police added. Earlier, Police said 12 security personnel were injured in a landmine blast triggered by Maoists in Sukma district of Chhattisgarh in the beginning of this month. India's home ministry has already stated that Maoist rebels continue to pose major threat to country's national security as they continue to target security forces and political leaders. The Maoist rebels are active in 83 districts spread across nine states of India. Maoist rebels have been fighting in several Indian states for more than 40 years claiming they have been inspired by the Chinese revolutionary leader Mao Zedong. Indian Prime Minister Manmohan Singh has already described the Maoist rebels as India's biggest internal security challenge.