Bieber was another multiple winner, picking up best pop act and top male singer.
Much of the attention in the run-up to the awards has been on the 17-year-old, who has denied allegations made by a US woman that he fathered her child when he was 16.
Accepting the second of his awards, he said: "There's been a lot of crap talked about me lately, but I've pulled through."
The cherubic pop star had earlier avoided media questioning, declining even to pose on the red carpet with his girlfriend, host Selena Gomez, when they arrived for the awards.
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