At the weekend, thousands of villagers backed by armed Maoists torched police stations and the ruling community party offices and killed three of the party's workers.

The attacks took place in villages near Lalgarh, which has virtually been under the control of the Maoist-backed People's Committee Against Police Atrocities since November.

The rebels say they are targeting the state's long-running communist government for alleged atrocities against farmers.

They have also been protesting against the construction of a steel plant near Lalgarh. India's premier Manmohan Singh has called it one of the gravest threats to the country's security.