Associated with the Maoist movement for more than 35 years, Azad was allegedly involved in attempts on the lives of two former state chief ministers, and carried a reward of 1.2 million rupees ($25,000) on his head.

'Greatest internal threat'

in depth

  India's costly war against Maoists
  India's battle against the Maoists
  Q&A: The Maoists of India
  Indian villagers take on Maoists
  Timeline: Major Maoist attacks

His killing came days after the Maoists shot dead 26 membersof the paramilitary forces in an ambush in the eastern state of Chhattisgarh.

Maoist rebel groups have fought for decades throughout east and central India against government rule.

Last year, the Indian government launched a major offensive to tackle the worsening left-wing insurgency, but since then the Maoists have hit back with a series of high-profile attacks.

Manmohan Singh, India's prime minister, has called the Maoists the country's greatest "internal security threat".

The rebels say they are inspired by the late Chinese communist revolutionary leader Mao Zedong.

They have tapped into the rural poor's growing anger at being left out of the country's economic gains and are now present in 20 of India's 28 states. They have an estimated 10,000 to 20,000 fighters.