NEW DELHI, April 22 (Xinhua) -- At least eight people were killed and more than four others injured in a crude bomb explosion in the eastern Indian state of West Bengal on Saturday, a police official said.

"The incident took place when the victims were making the bombs in a house at Tarka village in the state's Birbhum district in the afternoon. The death toll may go up as some of the injured are in critical conditions," the official said on condition of anonymity.

According to police, the bombs were being made for mafia gangs that were attacking each other at neighboring Darbarpur village.

"These groups have been hurling crude bombs at each other in a turf war over illegal sand mining. Most villagers fled the area because of the attacks. The victims were making bombs for one of the two groups locked in the so-called turf war," the police official said.

Local TV channels reported that the impact of the explosion was so severe that some of the victims were blown into parts which were thrown across the place.

A massive police force has rushed to the spot, the official said, adding that efforts are on to nab members of the two illegal mafia groups.

The explosion came a day after some seven people were killed in another crude bomb explosion in the district's Labhpur area.