Bieber fever? Or baby fever?

Justin Bieber has been hit with a paternity law-suit by a 20-year-old California woman, who is claiming that the underaged singer is the father to her 3-month-old baby boy.

According to the most recent issue of Star magazine, Mariah Yeater said that she and the 17-year-old had sex backstage at one of his Los Angeles shows last year. She wants him to take a paternity test "to scientifically confirm" that he is the father to her child and so that he could start providing financial support.

Bieber and his reps have been vigorously dismissing and denying the allegations. The pop sensation tweeted on Nov. 2, “all the rumors...the gossip....Im gonna focus on the positives....the music.”

Justin Bieber (creative commons)

Despite Bieber and his reps’ efforts to deny the accusations, a court hearing has been set for December.

People magazine reported that “Team Bieber” has not even seen the legal papers yet. “While we haven't yet seen the lawsuit, it's sad that someone would fabricate, malicious, defamatory and demonstrably false claims,” a rep for Bieber said in a statement. “We will vigorously pursue all available legal remedies to defend and protect Justin against these allegations.

Yeater claims that she was approached by a security guard while seated in the front row of the star's concert and asked if she wanted to meet the singer backstage, according to Britain’s Daily Mail.“I agreed to go with him and on the walk to a private area, he told me he wanted to make love to me and this was going to be his first time,” Yeater wrote in a statement, “We went inside and immediately his personality changed drastically. He began touching me and repeatedly said he wanted to f*** the s*** out of me.”

Yeater, who was 19-years-old at the time of the incident, will also be charged with statutory rape of a minor and would be at least guilty of a misdemeanor if these claims are true.

Bieber has been dating fellow teen superstar Selena Gomez. They went public at the Oscars in March, and are known for their public displays of affection. The two have also recently adopted a dog together.

In the February issue of Rolling Stone, the “Never Say Never” singer, who is a Christian, also said, “I don't think you should have sex with anyone unless you love them."

Reach writer Alisa Kim here