Jaden Smith has denied launching a foul-mouthed rant at a female fan online.

A message appeared on an Instagram account believed to belong to the 14-year-old Karate Kid actor, who is the son of Will and Jada Pinkett-Smith, featuring a string of obscene language.

The message read: "Bitch ass nigga lil ass girls stop hiding Android stank pussy ass lil girl the whole sea live in yo pussy wanna be MSFTS can't afford to get ya hair did but you f**king with my fans get ha get your life together (sic)."

The comment, which was posted by what is believed to be the young star's handle @letsmakeitdotorg, came in response to a fan who said: "Let me shut Up Yo" after the account holder initially stepped in when she called another fan fat in a heated debate.

Jaden quickly took to his official Twitter account to deny the rant was posted by him.

He wrote: "I Would Never Say Anything Like That To Anyone Let Alone A Women I Stand For My Republic Msfts Over All."

A spokesperson for the actor also told gossip website GossipCop.com: 'This was 100% not him."

Some of the actor's fans believe the message was posted from a parody of Jaden's Instagram account, which uses a lower-case L in place of the I in the handle.