Police are investigating claims that Justin Bieber headbutted a man after fighting two bartenders at a West Hollywood restaurant.

The 22-year-old singer was reportedly involved in an altercation with the three men at Serafina Sunset on Sunset Boulevard on Saturday at around 2am.

The LA County Sheriff’s Department said it received a battery report accusing Bieber of assaulting all three men.

“The witness said he broke up the fights and asked Mr Bieber to leave. Mr Bieber refused to leave and remained at the restaurant,” police said.

“The witness stated, a few minutes later, he saw Mr Bieber arguing with a patron, when Mr Bieber suddenly headbutted the patron.”

The alleged brawl comes just a day after Cleveland Police confirmed they were investigating the Baby singer for a separate incident.

Bieber has been accused of punching a man three times at a hotel after a basketball match last June.

Rodney Cannon claims he was attacked by the pop star and his bodyguards after he tried to take a photo with Bieber.

Bieber had previously warned fans he would no longer take pictures with them because they make him “feel like a caged animal”.

No charges have yet been filed against Bieber regarding the restaurant altercation, with both bartenders and the restaurant reportedly refusing to file a report.

The restaurant’s director of public relations Caroline McBride said: “We know very little about the alleged incident at Serafina Sunset with Justin Bieber.”

“We always have pleasant experiences with Mr Bieber whenever he comes to Serafina.”