The Maoists, who are very active across much of India, claim to be fighting on behalf of peasants, farmers and labourers, demanding land and jobs. They are active in almost half of India's 28 states.
The rebels have called for people to boycott the upcoming polls to elect a new parliament.
Thousands have died as a result of the Maoist insurgency in India. The rebels are also known as Naxalites, derived from Naxalbari - a village in North Bengal where peasants rose up in an uprising in 1967, triggering a countrywide upheaval.
Manmohan Singh, India's prime minister, has described the insurgency as one of the greatest threats to India's domestic security.