Justin Bieber got the 40th annual American Music Awards prizegiving underway in Los Angeles on Sunday (18Nov12) by picking up the night's first trophy.

The Baby singer was named Favorite Pop/Rock Male Artist at the top of the show, just after fellow nominee and mentor Usher opened the ceremony with an energetic medley of recent hits, including Numb and Can't Stop.

Bieber's win was his fifth Ama. He's nominated for three more prizes at the 2012 event.

The pop superstar dedicated his award to "all the haters who thought that maybe I was just here for one or two years; I feel like I'm gonna be here for a very long time."

He also took a moment to thank his "amazing, beautiful" mum, Pattie Mallette, who accompanied him to the big event, and manager Scooter Braun.

Taylor Swift followed up Bieber's big win by claiming the Favorite Female Country Artist prize.

The Love Story singer beat out Miranda Lambert and Carrie Underwood to claim her fifth straight win in the category and her 11th Ama overall.