The video was filmed in Nuku'alofa on Saturday night, soon after the country's rugby league side's victory over Samoa.
In the grainy 45 second video that's been viewed thousands of times, a police pick up truck is parked in the middle of an intersection with its blue lights flashing.
In the back, a burly officer is seen lifting the flailing body of a man to about waist height, before slamming him into the floor.
