Maoist guerrillas blew up a forest office on Saturday in West Bengal's West Midnapur district to apparently avenge the destruction of a "martyrs' memorial" by police.
The incident took place in Lalgarh village in Kantapahar area, about 200 kms from Kolkata.
"Eyewitnesses told us that a six-member group came and planted explosives inside the small forest office," West Bengal Inspector General of Police (Law and Order) Raj Kanojia told IANS.
He said the roof and portions of the wall of the office collapsed. Nobody was in the building when the explosion occurred.
The Maoists observed "martyrs' day" from July 28-30 and had set up a martyr's altar near Lalgarh that the police destroyed on Friday, police sources said.
Charu Mazumdar, the founder leader of the Indian Maoist movement, died in police custody in Kolkata on July 28, 1972. The day is marked Martyrs' Day.