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Look out, Justin Bieber: Demi Lovato is on the "attack"!

Demi, who currently is burning up the charts with her hit "Heart Attack," dissed Justin on multiple occasions at The X Factor auditions on July 10, according to TMZ.

The first slam was a subtle one and was directed at a 22-year-old contestant who was giving the judges a lot of attitude during his audition.

Credit: Ray Mickshaw/FOX ©2011 Fox Broadcasting Co

"We don't need another little punk running the streets," Demi reportedly told the contestant.

Later, Demi made it even more clear that she's not a Belieber. When a young man auditioned with Justin's hit, "As Long As You Love Me," Demi squeezed in a harsher crack at Justin's expense.

"Well, finally someone can sing the song the way it was meant to be sung," Demi told the guy. Ouch!

So what's up with Demi getting in all these digs at Justin? Well, we know that Demi and Selena have been besties since meeting more than ten years ago on the set of Barney & Friends, so maybe she's not too pleased with how Justin has treated Selena.

Clearly, Demi does not want Selena to get ready to come and get Justin's love.

Source: TMZ