WTF! JUSTIN BIEBER IS A RAPPER NOW?

Justin Bieber has already conquered the pop world. Now the teen singing sensation is trying his luck as a rapper.

Bieber, under the alias "Shawty Mane," released a video showing off his secret rap skills on his Twitter page Wednesday night.

He announced the video to his more than five million Twitter followers, "speaking in tongues freestyle ... who knew i could rap lol ... my alter ego rap name is Shawty Mane.. hah."

The video, posted on Twitvid.com, already has been watched more than 300,000 times.

The 16-year-old Canadian singer rapped over a beat made popular by Harlem rappers Vado and Cam'ron. The original song, "Speaking in Tungs," appears on Vado's album, "Slime Flu," released on Tuesday.

Shawty Mane still wears Bieber's signature floppy hairstyle in his rap persona. But he's tossed on a pair of glasses that closely resemble the specs of rap legend, Daryl "D.M.C." McDaniels, of Run DMC, and he wasted no time before delivering his first rap diss.

The target: New England Patriot's quarterback Tom Brady.

"Call up Mr. Brady. Tell 'em leave his hair to the guy who sings Baby," spits Shawty Mane, while faking throwing a football and running his fingers through his hair.

"All right, stop, drop and roll, Justin Bieber is on fire, it's time to realize, it's time to call me young sire," he continues.

"I just wanted to do this just to prove, that you know, I got skills on the rap game," he said at the end of the nearly two minute video, where he even rhymes ka-ka with Gaga.