Teen sensation Justin Bieber upset two Maryland state troopers ahead of his concert on Sunday after throwing water balloons at them.

A police spokesperson claims the Canadian was "horsing around with members of his staff" before his sold-out gig at the Maryland State Fair, and hurled the balloons, filled with water, at two officers who were controlling the crowds.

One of the balloons hit a cop's gun belt and burst, while another balloon bounced off the other trooper.

The officers decided not to write up a report but the police representative has deemed the Baby hit-maker's actions "inappropriate behavior".

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