At least 12 insurgents were killed in combat with Indian troops in the eastern states of Orissa and Jharkhand on Sunday, police said.
Police teams raided a forested region in Orissa's southern district of Rayagada late Saturday night following a tip, dpa reported.
"The gunbattle continued overnight and bodies of nine Maoists were recovered from the scene on Sunday," Rayagada deputy police chief PK Bhoi said by phone.
Rayagada, considered a Maoist stronghold, is situated more than 400 kilometres south-west of state capital Bhubaneshwar.
Three insurgents were also killed in neighbouring Jharkhand state's Bokaro district, the PTI news agency reported.
They included two self-styled area commanders, police officials told the agency.
More than one-third of India's 626 administrative districts are affected by the insurgency, which Prime Minister Manmohan Singh has described as the main internal security threat.
The rebels claim they are fighting for the rights of tribal, landless and poor people in some of the country's poorest regions.
At least 1,174 rebels, troops and civilians were killed in incidents related to the insurgency in 2010, making it one of the deadliest years in the four-decade old rebellion in India.