The Canadian star performed a free show in the Norwegian city on Wednesday (May 30) as part of a 'secret' European promotional tour.

Prior to the show the singer took to Twitter to call on fans to respect police wishes as he believed their safety might be at risk.

TMZ reports that Olso mayor Fabian Stang told them an investigation is underway after scores of girls were injured on the day, with enthusiastic fans seen chasing Bieber through the streets. He said:

"I have already called on the Emergency Planning Agency to examine the entire event from the planning stage to its implementation. We have to find out what went wrong and why it happened."

Bieber meanwhile posted video footage of himself fleeing his fans on water after they chased him in boats.

The Canadian star performed a free show in the Norwegian city on Wednesday (May 30) as part of a 'secret' European promotional tour.

Prior to the show the singer took to Twitter to call on fans to respect police wishes as he believed their safety might be at risk.

TMZ reports that Olso mayor Fabian Stang told them an investigation is underway after scores of girls were injured on the day, with enthusiastic fans seen chasing Bieber through the streets. He said:

"I have already called on the Emergency Planning Agency to examine the entire event from the planning stage to its implementation. We have to find out what went wrong and why it happened."

Bieber meanwhile posted video footage of himself fleeing his fans on water after they chased him in boats.

Bieber confirmed the show on Twitter earlier today (May 30) but stressed that fans must listen to the police otherwise their safety may be jeopardy.

He is set to perform a TV special show tonight (May 30) in Oslo at the Opera House. He tweeted:

"NORWAY - please listen to the police. I dont want anyone getting hurt. I want everything to go to plan but your safety must come first. Here r the details...at 920 2nite Im going to do a free show 4 u the fans at the Opera House here in Oslo. The show is part of my #AroundTheWorld TV special and I will be doing 6 songs, 4 new, 2 old before i leave. BUT...."

He continued: "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 and tonight we will have some fun. love you and im excited to see you all. NORWAY...THANK YOU FOR HAVING ME! #BELIEVE."