Canadian teen sensation Justin Bieber performed his third night at London's O2 Arena this evening (March 7), but worried fans after he was rushed off stage during his set.

Social networking site Twitter became inundated with concern for the 'Boyfriend' superstar and concert-goers were reporting that he had been visibily struggling during the performance.

One fan, Taylor Bell (@TaylorKarenBell), gave Pressparty an update on what happened to the young singer and explained that his manager, Scooter Braun, walked out in front of the arena to reassure fans that Bieber was alright:

"He said he couldn't breathe and he is backstage with a doctor at the moment! Scooter and Jayden come out and said! @Pressparty they said he will be able to finish the show though so it's okay!xx"

Another Belieber at the show tweeted: "Justin Bieber collapsed on stage in the middle of beauty and the beat and scooter came on and said he's with a doctor omg drama at the 02."

Someone else from the event added: "Bieber's manager Scooter just came out to tell us that @justinbieber is intent on finishing the show despite being unwell #BelieveTour."

Check out footage of Scooter Braun telling the arena that Bieber needs medical attention for something that may be wrong with his lungs, but wanted to finish the concert here.