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And here we thought Tuesday's big Justin Bieber news was the spiky new coif he debuted on "The Tonight Show." Star magazine (via Radar Online) claims a 20-year-old woman has filed a paternity suit against the 17-year pop idol, contending he's the father of her 3-month-old son and demanding he take a DNA test.

But the Belieber army shouldn't get stabby with murderous rage just yet: Justin's camp adamantly denies the accusations made by one Mariah Yeater, who alleges she had a brief, backstage encounter with the now Selena Gomez-dating singer after his concert at the Staples Center in Los Angeles on Oct. 25, 2010.

For those keeping track, he was 16 at the time, two years below California's age of consent.

"All the rumors...the gossip.... I'm gonna focus on the positives ... the music," Bieber tweeted on Wednesday morning, along with a link to his new Christmas album.

Yeater's version of events reportedly goes something like this: At the show, Bieber's bodyguard singled her out and asked if she'd like to go backstage, where she waited for him with "several young women."

(And if you think this is starting to sound like that Jonas Brothers episode of "South Park," you're not alone.)

She claims a chat with Justin made it "immediately ... obvious that we were mutually attracted to one another, and we began to kiss." Then, she says, Justin suggested they go someplace more private.

That purported place? A bathroom, where -- oy, must ... force ... fingers ... to ... keep ... typing -- she supposedly, ahem, punched Bieber's V-card.

Mariah (double oy) now wants Justin "to scientifically confirm" the supposed spawning and "provide adequate support for my baby."

But she should prepare for the full force of Team Bieber to come down on her claims.

"While we haven't yet seen the lawsuit, it's sad that someone would fabricate malicious, defamatory and demonstrably false claims," the star's rep tells Wonderwall in a statement. "We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations."

Adds a source to People, "The kid is never alone. There's always someone with him. He's never met this woman."


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