Selena Gomez drops F-bomb, walks off stage during Jingle Ball performance

Dec. 8 (UPI) -- Selena Gomez was so frustrated by technical difficulties during KIIS-FM's annual Jingle Ball in Los Angeles Friday night, that she said "what the f***?" into the mic and left the stage.

One eyewitness said it "looked like" Gomez was lip syncing from the start of her performance and kept playing with her ear piece.

During what The Hollywood Reporter described as a "heavily backed rendition" of the track, "Undercover," Gomez swore into the mic.

"Sorry, the sound isn't working!" she told the crowd (as seen in this video). "Are you guys having a good night?"

"I promise, a lot cooler people are gonna come out tonight," she added. "Is it okay if I perform two more songs and you guys can get to it?"

"I have to thank you guys so much for allowing me to be able to perform the music that I love," Gomez said when her sound didn't improve. "And I have to say that before you guys go on to the people that you care about, I really appreciate you supporting everything that I do. So this next song is the first song I had hit No. 1, and it's called 'Come & Get It.'"

Gomez then left without finishing her last song.

[E! News, The Hollywood Reporter, Us Weekly]