(Reuters) - Canadian pop star Justin Bieber ran headlong into trouble on a European promotional tour on Thursday, knocking himself out backstage in Paris and dealing with a crushing crowd in Norway that left some fans injured one day earlier.

Thursday's incident occurred after the singer fell into a glass wall during an intimate concert in Paris. Bieber told celebrity news website TMZ.com he felt lightheaded but was able to perform his last song before going backstage and passing out for 15 seconds.

TMZ posted an audio clip of its conversation with the pop sensation in which he said doctors told him he suffered a concussion and ordered him to relax. The singer quickly posted on Twitter that he was doing well, joking about the incident and saying "gotta laugh at yourself sometimes."

The concussion comes one day after Bieber, on a brief tour of major European cities to promote upcoming album "Believe," was met with a crush of fans before a free concert in Oslo leading to reports of dozens of young girls being injured.

Bieber's record label, Universal Music, said in a statement to celebrity site E! Online on Thursday that it "regrets strongly that some of those who were Justin concert had a bad experience."

A label executive said "fortunately no one was seriously injured," and added that Bieber wanted to return to Norway and perform a future concert there.

Calls and e-mails to Bieber's representatives were not immediately returned.

Bieber performed a free, six-song concert at the Oslo Opera House on Wednesday that is planned to be featured on his upcoming one-hour NBC television special to be aired next month.

The 18-year-old singer was forced to tweet a safety message ahead of the show after police were unable to control the crowds of fans trying to catch a glimpse of the star.

"for the show to happen u must all listen to the police. we are all concerned for your safety and i want what is best for u. please listen," Bieber posted to his 22 million Twitter followers on Wednesday.

TMZ said 49 young girls were injured and 14 taken to hospitals, and police came close to declaring a state of emergency in the capital. Those reports could not be immediately confirmed.

This is not the first time Bieber fever has caused crowd control and safety issues. In November 2009, fans stampeded a shopping mall in Long Island, New York ahead of an appearance by the pop star, forcing organizers to cancel the event.

Bieber's manager was charged with reckless endangerment and criminal nuisance, but the charges were later dropped.