Oscars ends in chaos after film mix-up

African-American coming-of-age tale Moonlight has been awarded the best picture Oscar after La La Land was handed in an unprecedented mix-up.

Warren Beatty and Faye Dunaway took to the stage to announce the winner with Beatty hesitating as he prepared to read the name.

He handed the envelope to Dunaway who read out La La Land to rapturous applause sparking celebrations among the cast and crew.

As the casts of both films stood awkwardly on stage, Beatty explained he had been given the wrong envelope to open.

"I want to tell you what happened. I opened the envelope and it said, "Emma Stone, 'La La Land.'"

"That's why I took such a long look at Faye and at you. I wasn't trying to be funny," Beatty said, breaking into tense laughter. It was Dunaway who ultimately said La La Land.

"It is true. It's not fake," said "Moonlight" director Barry Jenkins. "My love to 'La La Land,' my love to everybody."

It was the first time in living memory that such a major mistake had been made at the Academy Awards, Hollywood's biggest night.

"Is that the craziest Oscar moment of all time?" Stone, who won the best actress Oscar for her La La Land role as a struggling actress, told reporters backstage "It's a very strange happening for Oscar history."

"I think everyone is in a state of confusion ... and so excited for Moonlight," Stone added, saying it was "one of the best films of all time."

La La Land went into the Oscars with a leading 14 nominations and emerged with six, including for its score and theme song City of Stars.

La La Land director Damien Chazelle, 32, became the youngest person to ever win a best director Oscar.

Manchester by the Sea star Casey Affleck was named best actor.

"Man, I wish I had something better and more meaningful to say ... I'm just dumbfounded that I'm included," said Affleck, a first-time Oscar winner.

Affleck came through despite 2010 sexual harassment allegations that resurfaced during awards season. Affleck denied the allegations which were settled out of court.

Viola Davis and Mahershala Ali won their first Oscars for their supporting roles in African-American stories Fences and Moonlight, in stark contrast to the 2016 Academy Awards when no actors of colour were even nominated.

Moonlight, about a young boy struggling with poverty and his sexuality, also won the best adapted screenplay statuette, while grief-driven independent drama Manchester by the Sea took home original screenplay.

US President Donald Trump was the butt of numerous jokes, capping an awards season marked by fiery protests at his policies.

Kimmel fired off political zingers and even tweeted at the Republican president, getting no immediate response.

But for the most part speeches were mild or made general pleas for tolerance rather than directly attacking Trump.