Will Smith slaps Chris Rock on Oscar stage

Minutes later, when accepting his first Oscar on Sunday night for best actor for his role in King Richard, Smith apologised to the Academy of Motion Picture Arts and Sciences and his fellow nominees in a tear-filled acceptance speech, but not to Rock.

"I want to be a vessel for love," Smith said, with tears streaming down his face during his acceptance speech.

It was unclear whether Rock, a comedian and actor, was aware that Smith's wife, Jada Pinkett Smith, suffers from a disease that causes hair loss.

The episode with Rock, upstaging the rest of the 3-1/2 hour show, was sure to become one of the most memorable moments in 94 years of Academy Awards.

The Academy did not say whether Smith would be invited back for future shows, but said on Twitter, "The Academy does not condone violence of any form."

In a statement sent to media, and without naming names, Los Angeles police said investigators were aware of the incident, but that, "The individual involved has declined to file a police report."

Should Rock change his mind, however, LA police would investigate.

The incident at first appeared to be a scripted joke but turned serious when Smith shouted: "Keep my wife's name out of your f***ing mouth."

The audio from the show, broadcast on a time-delay of a few seconds in the United States, appeared to have been cut from the live transmission for many viewers because of the language. But it was audible in some broadcasts, for example in Japan and Australia.

Rock was roasting some of the nominees and, after mentioning Smith, said of his wife, "Jada, I love you. 'G.I. Jane II,' can't wait to see it."

He was referencing the 1997 film "G.I. Jane" in which actress Demi Moore shaved her head.

Smith then walked on stage toward Rock, who had his hands behind his back when Smith threw an open hand at his face that produced an audible smack, and in a form befitting an action movie star. Rock somehow stayed on his feet.

"Oh, wow! Wow! Will Smith just smacked the shit out of me," Rock said as the audience laughed, thinking it was a skit. "Wow, dude. It was a 'G.I. Jane' joke."

Smith then made what may become one of the most repeated phrases of Oscar history when he said, "Keep my wife's name out of your f***king mouth."

Rock responded, "I'm going to. That's the greatest night in the history of television."

Smith then repeated his phrase, louder and more deliberately.

Jada Pinkett Smith told Billboard in December she has been battling the autoimmune disorder alopecia, which can cause hair loss and balding.

The audience initially thought Smith's indignation was feigned, part of the act.

It was only after he returned to his seat and shouted that the audience went silent and audibly gasped.

Smith, 53, has been one of Hollywood's most charming and bankable stars, and was known for his clean rap lyrics when he shot to fame in the 1990s in the television sitcom The Fresh Prince of Bel-Air.

He took on mostly comedy and action roles early in his movie career before expanding into drama, and twice had been nominated for best actor before, for 2001's Ali and the 2006 movie The Pursuit of Happyness.

Smith won this time for playing Richard Williams, the father of tennis stars Venus and Serena Williams.

"Richard Williams was a fierce defender of his family," Smith said through tears in an obvious reference to what had just taken place.

Smith did not mention Rock but said: "Art imitates life -- I look like the crazy father, just like they said about Richard Williams. But love will make you do crazy things."

And his final remark before leaving the stage was, "I hope the Academy invites me back."

Australian Associated Press