U2 frontman Bono injured his back while preparing for the next leg of the band's "360" tour which is scheduled to kick off June 3rd in Salt Lake City, Utah. The 50 year old Irish singer has undergone emergency surgery at a Munich hospital. A spokesman for the band released the following statement:

"Bono has today undergone emergency back surgery for an injury sustained during tour preparation training. He was admitted to a specialist neuro surgery unit in a Munich hospital. Bono will spend the next few days there, before returning home to recuperate. Once his condition has been assessed further, a statement will be made regarding the impact on forthcoming tour dates."

U2's "360" tour was the top grossing tour in the world, bringing in $109 million, and it is predicted that it will end up the highest grossing tour in history. U2 has sold more than 150 million albums worldwide and is one of the most successful musical acts in history.