'Biggest threat'

Rohit Singh, an Indian journalist, told Al Jazeera that this was one of the most brutal attacks to take place against the security forces by Maoists. 

"The Maoists are very worried by the central and state government military operation against them. They are very angry and want the operations against them to stop immediately. 

"They want senior Maoist leaders captured by the government in the last couple of months to be released."


 Q&A: The Maoists of India
 India's battle against the Maoists

The Maoists, described by Manmohan Singh, the country's prime minister, as the country's biggest internal security threat, regularly ambush police, and attack railway lines and factories aiming to cripple economic activity.

Indian authorities have launched an offensive against the rebels entrenched in the forests of the so-called "Red Corridor" that stretches across  north and eastern India.  

Chidambaram hardened his rhetoric at the weekend after 10 policemen were killed in a landmine attack in eastern Orissa state, calling the rebels "cowards". 

String of attacks

On Monday, he said the Maoists were the "first enemy" of the country.  

In March 2007, the Maoists were blamed for an attack that killed 55 policemen in Chattisgarh.

In February, at least 25 policemen were killed in eastern West Bengal when Maoists attacked a camp.  

The Maoists are also known as Naxals, after their first armed uprising, which took place in a small village called Naxalbari in the Indian state of West Bengal some 40 years ago.