The incident, which took place in an area under the Gingaso police station, was caught on camera by an amateur videographer and later released to the media.
In the footage, the policemen, seen in plainclothes, were identified as station in-charge Mahendra Singh and two other constables belonging to the same police station.
The truck driver had been stopped by the police, who said they were checking for contraband items.
The driver claimed he was transporting lentils, and the policemen asked for a bribe which he refused to pay.
All the policemen have been suspended.
The driver has been discharged after being given first-aid.