Around 20 people hurled bombs inside the premises of a church, located near Karimpur-Chapra highway along the India-Bangladesh border at Maliapota, before storming the prayer hall where midnight mass was being held with about 1200 devotees, DIG (HQ) N C Ghosh said in Kolkata on Wednesday.
The gang looted money from the church safe and also wristwatches and other valuables from the devotees before escaping under the cover of darkness and fog.
Ghosh said the police chased them and fired at least 10 rounds.
The chief priest suffered cuts in his hand while resisting the attackers. Five others were injured.
The mass, which was disrupted, resumed later.
The DIG said a search was on to track down the attackers and five persons had been detained for interrogation.
Police pickets were posted around the church and reinforcements were sent, while senior officials were camping at the spot.
Meanwhile, security was tightened around churches throughout the state.
