Justin Bieber Flashed His “6-Pack” Abs to Rihanna!

 Johnny Nunez/WireImage.com; Jason Merritt/Getty Images

Apparently, Justin Bieber has a major Situation — and Rihanna's seen it!

On Monday, Rihanna, 22, Tweeted: "Justin Bieber just flashed me his abs in the middle of a restaurant! Wow! He actually had a lil 6 pack! Sexy,lol!"

An insider confirms to UsMagazine.com that Rihanna and the 16-year-old singer had dinner that night in Manhattan with record exec L.A. Reid and other pals.

As the meal progressed, "Justin started bragging about how he has abs. Everyone started laughing but Justin was serious," says the source.

Eventually, Rihanna and her pals jokingly asked Bieber to show them.

"Justin took off his jacket, glasses and lifted up his shirt," the source explains. "Apparently he does have a little 6 pack!"

Adds the insider: "The table was hysterical."

When the "Only Girl" singer Tweeted the news, Bieber pleaded: "'You have to say it was sexy if you tweet it. You know it was sexy!'"

Rihanna will hit the stage this Sunday at the Nokia Thater in L.A. — opening up the American Music Awards. UsMagazine.com has learned exclusively that she'll debut her live rendition of "Love the Way You Lie Part ii," followed by her number one smash "Only Girl (in the World)."

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