"Crash" and "Brokeback" each won three Oscars, but Paul Haggis's study of racial prejudice took the top prize while "Brokeback," a love story about two gay cowboys, had to settle for the best director statuette for Taiwan's Ang Lee.

"Walk the Line" star Reese Witherspoon, and "Capote" frontman Philip Seymour Hoffman scooped the top acting awards, while US screen idol George Clooney and Britain's Rachel Weisz won Oscars for their supporting roles in two politically charged movies.

"Thank-you for embracing our film about love, about tolerance and about truth," said "Crash" co-producer Cathy Schulman in a year dominated by either low-budget and independent films.

"Brokeback," which rose into the Oscars ceremony armed with a leading eight nominations, had for weeks been the clear favourite to win the best picture and up to four other awards.

But it was "Crash," a complex jigsaw of a story about the lives of six ethnically-diverse people whose lives collide in a Los Angeles car crash, that stole the show by making good on three of it six nominations.

"We are humbled by the other nominees in this category you have made this year one of the most breathtaking, stunning maverick years in American cinema," Schulman said, after accepting the best picture statuette from actor Jack Nicholson.

Though "Crash" and "Brokeback" stole the main honours, two big-budget studio spectaculars also won three Oscars each: Peter Jackson's 200-million-dollar "King Kong" and Rob Marshall's "Memoirs of a Geisha," which each won in technical categories.

"Crash," which cost just 6.5 million dollars to make, also won the best original screenplay award for Haggis and Bobby Moresco as well as a film editing statuette.

The 14-million-dollar "Brokeback" also picked up the Oscars for best adapted screenplay that went to Diana Ossana and Larry McMurtry and best original score for Argentine composer Gustavo Santoalalla.

Lee, 51, the first Asian to win the directing Oscar, highlighted the groundbreaking topic raised by Annie Proulx's short story.

"There names are Ennis and Jack and they taught all of us who made 'Brokeback Mountain' so much about not just the gay men and women whose love is denied by society, but, just as important, the greatness of love itself."

Hoffman, 38, made good on his first nomination to win best actor for his searing performance as eccentric author Truman Capote, while Witherpoon won best actress for her turn as country music singer June Carter Cash in "Walk the Line."

Clooney only cashed in on one of his three nominations on Sunday, scooping the best supporting actor Oscar for playing an ageing CIA spy in "Syriana". The heavily-pregnant Weisz won the best supporting actress award for her role in "The Constant Gardener."

Clooney's film tells of US machinations in the Middle East oil industry, while Weisz played an activist battling pharmaceutical-industry human rights abuse in Africa.

Weisz, 34, praised her co-star Ralph Fiennes and novelist John LeCarre, who wrote the story of immoral big business on which the film was based.

She said his "unflinching, angry story really paid tribute to the people who are willing to risk their own lives to fight injustice. They are greater men and women than I," the actress said.

The politically outspoken Clooney, 44, was the big star of this year's Oscars. He came to the ceremony armed with three nominations, as best supporting actor for "Syriana" and best director and original screenwriter for "Good Night, and Good Luck."

"Alright, so I'm not winning director," the heartthrob quipped. "This object will always be synonymous with your name: 'Oscar winner George Clooney,' 'Sexiest Man Alive 1997,' 'Batman,' dies today in a freak accident.'"

The South African movie "Tsotsi," a raw but compassionate depiction of a brutal gangster in a Johannesburg township, directed by Gavin Hood, won the best foreign-language film Oscar.

Other awards went to British claymation guru Nick Park for "Wallace and Gromit in The Curse of the Were-Rabbit."

The six-times nominated story "Memoirs of a Geisha," set in Japan, won its three statuettes for costume design, cinematography and art direction, while "King Kong" made good on three of its four nominations for sound editing, sound mixing and visual effects Oscars.

Clooney's political drama "Good Night, and Good Luck," which was up for six Oscars, failed to win any, with Clooney himself losing out on the awards for best director and best original screenplay.

"Munich," Steven Spielberg's epic about the aftermath of the Palestinian massacre of Israeli athletes at the 1972 Olympics also won no Oscars despite five nominations. "Capote" scored one out of five possible awards.