U2 have been forced to postpone the next leg of their world tour after singer Bono injured his back, the band has said.

The singer underwent emergency surgery in Germany after suffering an injury while preparing for the upcoming shows in the US.

Bono, who celebrated his 50th birthday in New York earlier this month, was treated at a specialist neuro surgery unit in a Munich hospital.

"Bono will spend the next few days there, before returning home to recuperate," the band said on their website.

Promoters Live Nation said the singer's sudden injury had forced the band to pull the plug on the latest 360 degree tour launch on June 3 in Salt Lake City.

U2's manager Paul McGuinness also posted a message to inconvenienced fans on the U2 website insisting the tour dates will be rescheduled.