"Thirty-seven special police officers and 16 personnel of state police died in the attack," Chhattisgarh Chief Minister Raman Singh told AFP.

  

'One of the worst'

The attack is "one of the worst" carried out by the insurgents, said Kanwar Pal Singh Gill, who was appointed security advisor to Chhattisgarh state government last April. Some local media reported the toll as high as 60.

 

Maoist rebels say they are fighting for the rights of neglected tribes and landless farmers. Tens of thousands of people have been displaced in Chhattisgarh and are now living in tent shelters as Indian counter-insurgency forces operate in the countryside.

  

New Delhi refuses to negotiate with the Maosists, wholaunched their armed campaign in 1967.

"The Naxalites are a very comprehensive and cohesive group that straddle 13 states and their common goal is to set up a revolutionary state in India ... there are a number of areas which are no-go areas for the state apparatus," General Ashok Mehta, a retired army general and Indian affairs analyst, told Al Jazeera.

 

Security threat

  

As a result, about 50,000 villagers have been displaced in the state and are now living in tent shelters as Indian counter-insurgency forces operate in the countryside.

  

Officials have said India's Maoist insurgency, which dates back over four decades, now threatens huge swathes of India's centre, east and south.

  

Last year, Manmohan Singh, the Indian prime minister, described the  Maoists as the single biggest threat to the nation's internal  security.

 

Some 669 people died in 2005 in violence linked to more than 9,000 armed rebels who have spread over 15 states, according to government estimates.

  

At least 372 people, including 154 civilians and 75 security force personnel were killed in Maoist-related violence in 2006, according to a security portal run by security advisor Gill.