Justin Bieber collapses during London concert

Justin Bieber collapsed backstage during a concert at London's O2 Arena tonight and was taken to a nearby hospital after finishing the show.

Sources tell TMZ that Justin felt woozy during the show and, with four songs left to perform, he stumbled backstage and collapsed.

Concertgoer Lauren O'Dell told E! News that Justin left the stage during "Beauty and the Beat" and the first sign that he was in distress came when he lay down on the stairs. "We all thought he was joking around," O'Dell said.

Emergency personnel reportedly treated him with oxygen and advised him to go to the hospital but he declined, insisting on finishing the show.

Concertgoers quickly posted videos of the situation to YouTube.

Justin's rep, Scooter Braun, and a surprise guest, Will Smith's teenage son, Jaden Smith, took the stage. "Justin's got very light breath. The whole show he’s been complaining, He’s backstage with the EMTs and the doctor," Braun told the crowd.

"They're telling him that they want him to go see somebody and see what's going on with his lungs."

But Justin came back out and finished the show to an ovation from the audience in the same venue where he was roundly booed after showing up two hours late for his concert earlier this week.

He was transported to the hospital after the concert and is reportedly receiving treatment.

"The fans were so supportive and cheering him on and chanting his name," O'Dell told E!. "He came back on and finished with 'Believe,' 'Boyfriend' and 'Baby,' but struggled with energy.

"We were really worried. The deejay songs were going out for awhile. We were wondering if something (more serious) happened."

Justin also fainted during a show in Paris last year.

Sources tell TMZ that the 19-year-old singer is feeling OK, but doctors want to evaluate his condition.

"tough kid," Braun tweeted later. "proud night. once again he always finishes the show. full out. true pro. now get better and rest up! strange night but proud nt."

| Lisa Gutierrez