The mayor of Oslo has called for an investigation into Justin Bieber's recent promotional event in Norway which is said to have left 49 teenage girls injured.

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.