Justin Bieber was rushed to a hospital in London moments ago ... after collapsing backstage during a concert ... TMZ has learned.
A source close to Justin tells us the singer felt woozy during the show at the O2 Arena ... and with 4 songs to go, he stumbled backstage where he collapsed.
We're told the singer was pulled into a private room where he was treated with oxygen from emergency personnel.
Sources say Bieber was advised to go to the hospital ... but declined ... insisting that he "had to finish the show for his fans."
That's when Bieber's rep, Scooter Braun, went on stage on told the crowd ... "Justin's got very light breath. The whole show he’s been complaining, He’s backstage with the EMTs and the doctor."
Read more and see Scooter Braun's on stage response at TMZ Here