Justin Bieber dismisses as rumors a fan's paternity suit that claims the Baby singer is the father of her three-month-old son.

Mariah Yeater, 20, alleges in the paternity suit that she met Bieber backstage at a concert at the Los Angeles Staples Center and had sex with him in a bathroom.

Bieber, who released his Christmas CD, Under the Mistletoe, this week, addressed the matter indirectly on Twitter Wednesday, writing, all the rumors … the gossip … I'm gonna focus on the positives … the music.

Yeater says Bieber -- then 16 -- told her he didn't want to use a condom because it was his first time having sex. She says in the suit, obtained by RadarOnline.com, that the supposed encounter lasted 30 seconds.

Yeater is seeking financial support and a paternity test from the pop star, but she could find herself in legal trouble if her claim is true. Yeater was at least 18 when she claims the sex occurred, but Bieber was 16. The age of consent in California is 18.

Bieber's rep said in a statement: It's sad that someone would fabricate malicious, defamatory and demonstrably false claims. We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations.

California Twitter Los Angeles Justin Bieber