Reportedly, JUSTIN BIEBER caught on film making tasteless N-word “joke” that is sparking controversy. VIDEO

According to the UK tab The Sun, Bieber 20, who counts actor Jaden Smith, 15, as one of his closest friends and pop superstar Usher, 35, as a longtime mentor— was caught red-handed on video telling a tasteless racist joke to pals.

 “Why are black people afraid of chainsaws?” he asks an unidentified female friend in the tape, believed to have been filmed when Biebs was 17 — an outtake from the "Never Say Never" documentary film.

 “Don’t even say it,” warns a male pal off-camera.

“Run, n***er, n***er, n***er, n***er!” Bieber says, hysterically laughing at his own joke.

Bieber’s team attempted to keep the offensive video under wraps— but apparently failed to do so, according to the UK tab.

Now the Twitterverse has exploded like an atomic bomb.