Watch: Jason Derulo punches man after he mistakes singer for Usher

Jason Derulo has been caught in an ugly brawl with two men in Las Vegas.

The singer punched and slapped the men after they referred to him as R&B singer Usher.

Trespassers told TMZ that Derulo went angry when the men yelled, "Hey, Usher! F**k you, b***h!"  that he 'punched' one of the men 'right in the face.'

The security instantly arrived before the matter got worse. According to TMZ's law enforcement sources, police were called to the Aria hotel in between the altercation.

Jason, who at that time was going to his hotel room, returned from the escalator when the unidentified swore, thinking he was Usher.