City cops are investigating a report the pop star allegedly assaulted a man in an incident that was captured on video.

The footage reportedly shows Bieber fighting a guy after a Cleveland Cavaliers basketball play-off game.

The alleged victim told cops Justin grabbed his sunglasses, and he proved his point by showing them a photo he took of the Baby singer holding the shades, according to TMZ.

He claims he was hospitalised with various injuries, including a concussion.

Law enforcement sources tell the outlet the investigation is ongoing and no charges have been filed.