U2 tour doubt after Bono undergoes emergency op

U2'S lead singer Bono has undergone emergency surgery after being injured while preparing for the next leg of the band's world tour.

The star was rehearsing in Munich when he suffered a back injury and was rushed to hospital. The 50-year-old had been preparing for the North American leg of the "360 Degree" world tour, which is due to kick off in Salt Lake City on 3 June.

"Bono has today undergone emergency back surgery for an injury sustained during tour preparation," his spokesman said. "He was admitted to a specialist neurosurgery unit.

"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."

After North America, the tour was due to head to Turin in Italy.

It was not immediately clear how badly the injury would disrupt the group's tour,which earned about $109 million (75m) in 2009, according to Billboard, making it the world's most lucrative. The music journal also predicted it would end up being the highest-grossing tour in history.

The band, with hits such as Sunday Bloody Sunday and Where the Streets Have No Name, are arguably the world's most successful. They have sold more than 150m records, according to unofficial estimates.