Justin Bieber has hinted milk was to blame for him being sick on stage.

The 'Boyfriend' hitmaker vomited in front of his fans - who are nicknamed Beliebers - on Saturday night (29.09.12) when he was performing 'Out of Town Girl' in Glendale, Arizona, on the first night of his 'Believe' world tour.

The 18-year-old singer turned his back on the crowd and threw up before running off stage and he later took to twitter to imply milk combined with his dance routines was the reason he was sick.

In a series of tweets, he wrote: ''Great show. Getting better for tomorrow's show !!!! Love u.

''and.... Milk was a bad choice! Lol (sic)''

Justin returned to the stage and managed to sing his 2011 hit 'Never Say Never', but he had to leave the stage again after attempting to perform the first few bars of Nicki Minaj collaboration 'Beauty and a Beat'.

He remerged and told fans: ''It's hard for me, you know, not feeling great and throwing up in front of a bunch of people.

''Will you love me even though I'm throwing up on stage? I wanted to give you my best show ever so do you mind if I finish it?''