GLENDAL, Ariz. - A bit of a rough night for Justin Bieber as the pop star kicked off the U.S. leg of his "Believe World Tour" in Glendale, Arizona.

Halfway through his rendition of the song "Out of Town Girl," the teen dream from Stratford, Ontario suddenly turned his back to the crowd, bent over and literally threw up on stage.

After making a quick exit, the Beeb soon returned and apologized to his startled fans, sheepishly asking "Will you love me even tough I'm throwing up on stage."

As the fans responded with shrieks of love, the show went on — and Bieber didn't disappoint, doing a complete performance.

The young superstar later suggested in a Twitter Tweet that drinking a lot of milk before doing his rigorous dance routines, combined with a case of the debut show nerves, likely caused his tummy troubles.