Justin Bieber rushed to hospital

Justin Bieber collapsed backstage at a London concert and was rushed to hospital.

The 19-year-old has recently been photographed smoking what appears to be marijuana and is rumoured to be involved in a lot of late night partying.

Justin's alleged carousing seems to have caught up with him as TMZ reports he passed out at his O2 Arena show Thursday night.

A source told the website the star felt lightheaded when he went backstage initially with four songs left to perform. He collapsed at that time and medical personnel gave him oxygen in a private room.

When staff advised him to go to hospital Justin apparently declined because he "had to finish the show for his fans."

While being oxygenated, Justin's manager Scooter Braun went onstage to inform the audience of the star's medical breakdown.

"Justin's got very light breath. The whole show he's been complaining," Scooter said.

"He's backstage with the EMTs and the doctor."

Following his initial treatment, Justin did close out his show and received a thunder of applause from adoring fans.

He was then rushed to hospital and is currently receiving treatment.

According to TMZ, Justin is cheerful, but doctors want to evaluate his condition further.