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 posted on Twitter. "Thanks for everyone pulling me thru tonight. Best fans in the world. Figuring out what happened. Thanks for the love."

In a video of the concert posted online, Bieber's manager appeared on stage Thursday night and told the crowd that the singer was feeling "very low of breath" but would return to finish the show, which he did.

The "Baby" singer is in London to perform four concerts at the O2 arena.

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.