'Undefeated' wins Oscar for best documentary feature

Undefeated won the Oscar for best documentary feature on Sunday, an inspiring story about a struggling high school football team in a poor Memphis neighbourhood. But the film also inspired a rare Oscar night expletive when one of its co-directors, TJ Martin, blurted out the word "fucking" during a short acceptance speech in which he praised his fellow nominees.

"We would like to acknowledge our fellow nominees, they have inspired us. They have inspired us in so many ways, they should be up here with us, actually, that'd be fucking amazing," Martin said.

The word was bleeped out for the television audience, and minutes later Martin apologised to reporters backstage.

"First and foremost I'd actually like to apologise for this. I don't think it was the classiest thing. It did come from the heart. It was out of spontaneity, it was completely accidental," Martin said.

Directed by Daniel Lindsay and Martin, the film chronicles how a charismatic volunteer coach turns the high school team and its players around after years of losses. The film has echoes of The Blind Side, the 2009 feature film in which a Memphis mother played by Sandra Bullock adopts a homeless black teenager and helps him achieve football stardom.

In a wide open field with no clear favourite, Undefeated beat off strong competition from Paradise Lost 3: Purgatory, about the fight of three convicted murderers to clear their names, and Hell and Back Again, detailing the struggles of a war veteran returning to civilian life.

Director Michael Moore championed non-fiction filmmakers on Wednesday night at a pre-Oscar event and attributed a growing appetite for the art form to a public starved for the truth.

The often controversial director, who won an Oscar for gun control movie Bowling for Columbine and scored the highest-grossing documentary of all-time with anti-war film Fahrenheit 9/11, was hosting a symposium for best documentary features and short subjects.

"We've been living in a time where people have been lied to a lot," Moore told Reuters.

"People are tired of it and they want the truth, and documentaries represent the truth."