Jay-Z Accused of Raping 13-Year-Old Girl in Diddy Lawsuit

5:08 PM PT -- Tony Buzbee, who filed the suit on behalf of Jane Doe, tells TMZ ... "Mr. Carter previously denied being the one who sued me and my firm. He even filed his frivolous case under a pseudonym. What he fails to say in his recent statement is my firm sent his lawyer a demand letter on behalf of an alleged victim and that victim never demanded a penny from him. Instead, she only sought a confidential mediation. Since I sent the letter on her behalf, Mr. Carter has not only sued me, but he has tried to bully and harass me and this plaintiff. His conduct has had the opposite impact. She is emboldened. I’m very proud of her resolve."

5:00 PM PT -- Diddy's lawyers tell TMZ … "This amended complaint and the recent extortion lawsuit against Mr. Buzbee exposes his barrage of lawsuits against Mr. Combs for what they are: shameless publicity stunts, designed to extract payments from celebrities who fear having lies spread about them, just as lies have been spread about Mr. Combs.  As his legal team has said before, Mr. Combs has full confidence in the facts and the integrity of the judicial process.  In court, the truth will prevail: that Mr. Combs never sexually assaulted or trafficked anyone—man or woman, adult or minor."

Jay-Z has been sued for drugging and raping a 13-year-old girl in a lawsuit tied to disgraced rapper, Diddy ... which the music mogul is calling "a blackmail attempt."

In the documents obtained by TMZ ... Jay-Z is named by an anonymous accuser, who says the rapper and Diddy drugged and raped her back in 2000.

The plaintiff, who is suing as Jane Doe, says the alleged assault occurred at an after-party following the MTV Video Music Awards.

The accuser originally filed a lawsuit against Diddy in October ... in which she claimed the Bad Boy Records founder and an unnamed celebrity proceeded to assault her -- while an unnamed female watched.

The accuser has since named Jay-Z as the other celebrity in the alleged assault, as she refiled her lawsuit against Diddy to include the "Empire State of Mind" rapper on Sunday.

Jay-Z's reps have responded to the lawsuit with a statement from the rap mogul ... who said he was determined "to expose [the accuser] for the fraud [they] are."

He continued ... "My only heartbreak is for my family. My wife [Beyoncé] and I will have to sit our children down, one of whom is at the age where her friends will surely see the press and ask questions about the nature of these claims, and explain the cruelty and greed of people. I mourn yet another loss of innocence. Children should not have to endure such at their young age. It is unfair to have to try to understand inexplicable degrees of malice meant to destroy families and human spirit."

Diddy -- who was arrested and indicted on charges of racketeering and sex trafficking back in September -- is facing a number of sexual assault allegations across various lawsuits.

He has previously denied all of the accusations made against him.