Singer and pop idol Justin Bieber was apparently rushed to a hospital during his Thursday night concert in London, the entertainment website TMZ is reporting.

Fans who were at the concert immediately went on Twitter and reported Bieber, 19, appeared to pass out mid-concert.

The singer was treated with oxygen from emergency personnel back stage and finished his concert performance, then was taken to the hospital.

Bieber's spokesman said the singer had been "very low of breath" during his performance at the O2 Arena, the website said.

Lately, Bieber has been taking a bashing from the media and other celebrities who have criticized his new shirtless look and for showing up two-hours late to a Monday London concert.

Bieber later apologized to his young fans – and their outraged parents.

The pop singer insisted he had been only 40 minutes behind schedule, and blamed "technical issues."

But, he added in a tweet to his 35 million followers: "There is no excuse for that and I apologize for anyone we upset. However it was great show and I'm proud of that."

Concertgoers said the teenage star appeared onstage just before 10:30 p.m., almost two hours after the anticipated start time. On Wednesday, an obviously agitated Bieber went on Twitter and sent out a dozen tweets defending himself and blaming the media and haters.

The Associated Press contributed to this report.