Selena Gomez and Justin Bieber were spotted kissing backstage at the Billboard Music Awards on Sunday night (19.05.13) after both singers had performed at the ceremony.The 'Beauty and the Beat' hitmaker and 'Come & Get It' singer were caught on camera getting cosy backstage at the MGM Grand Garden Arena in Las Vegas after they had performed during the annual ceremony.In the clip, Selena is seen rushing over to her ex-boyfriend and wrapping her arm around his neck as he leans in to kiss her on the cheek - less than a week after the 20-year-old beauty confirmed to a Boston radio station that she is single.During the pair's intimate moment, their close friend Taylor Swift - who was sat next to Selena during the show - watched on pulling funny faces and poking her tongue out before the actress was eventually tugged away by a member of her entourage.Justin, 19, was greeted with a crowd of boos as he took to the stage to accept the Mile Stone award earlier on in the evening and defended his win.Ignoring the angry roar from the audience, the teen heartthrob said: "I'm 19 years old, I think I'm doing a pretty good job. I really wanna say it should really be about the music. It should be about the craft, the craft that I'm making."This is not a gimmick. I'm an artist and I should be, taken seriously and all this other bull should not be spoken of."The on/off couple both arrived in Las Vegas on Saturday (18.05.13) and were spotted at the Cirque du Soleil's 'Love' show.A source previously told E! News: "The pair got close and comfortable in their seats while snacking on peanut M&Ms and Mike and Ikes candy."