Updated 10:35 PM ET
Justin Bieber is recovering after fainting backstage at a concert in London.
A spokeswoman for Bieber said late Thursday that the 19-year-old pop star was given oxygen and took a 20-minute reprieve after fainting backstage at London's O2 Arena.
"Getting better," Bieber later posted on Twitter. "Thanks for everyone pulling me thru tonight. Best fans in the world. Figuring out what happened. Thanks for the love."
Jazz Chappell, a 20-year-old concertgoer who brought her younger sister and her friend to the show, said a backup dancer helped Bieber off stage after he announced he couldn't breathe and needed water. She said many fans in the audience were gasping and crying, while others kept cheering for him to return.
"I thought, `Give the guy a break. He just fainted. He's not a performing horse. Let him rest a second,"' said Chappell.
In a video of the concert posted online, Bieber's manager, Scooter Braun, appeared on stage and told the crowd that the singer was feeling "very low of breath" but would come back to finish the show.
Chappell said Bieber, who's in London to perform four concerts at the O2, later returned and performed low-energy renditions of his hits "Boyfriend" and "Baby."
Braun later tweeted "everyone please give him a little space and he will be ok. Im sure he appreciates the support ... Tough kid proud night once again he always finishes the show. Full out. True pro..."
The incident caps a difficult week for Bieber. He was forced to apologize to outraged fans who accused him of taking the stage almost two hours late for his first concert at the O2 on Monday. He insisted he was only 40 minutes late and blamed "technical issues." He took to Twitter to vent his frustrations with the media's portrayal of the incident.