Superintendent of Police SMH Mirza said two pistols, a 'bhujali', 11 bombs, fake identity cards, a car fitted with red beacon and a fake permission to use such a car were seized from the five.
All the arrested, who included a father and a son, hailed from Rampurhat area of neighbouring Birbhum district.
The beacon fitted car was found before an eatery at Nababhat locality here last night, Mirza said.
Identifying themselves as CBI officers, they assaulted a policeman on duty there when he was was talking to the driver of a truck which had a punctured tyre and blocked a portion of the road.
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The arms were found inside the car.
The SP said the arrested persons confessed during interrogation that they used to loot money from people by impersonating as CBI officers.
Chief Judicial Magistrate Salim Ahmed Ansari remanded two of them to police custody while others were sent to jail.
The case would heard again on July 24.