The 86th Academy Awards show kicked off Sunday, as Hollywood's finest gathered after one of the fiercest Oscars races in years, with no clear frontrunner for the coveted best picture prize.

Harrowing historical drama "12 Years a Slave," 3D space thriller "Gravity" and 1970s crime caper "American Hustle" are hotly tipped to take the top prizes at the Oscars, the climax of Tinseltown's annual awards season.

Host Ellen DeGeneres opened with a monologue making fun of the storms which hit California on the eve of the Oscars, threatening to rain on the pre-show red carpet parade.

"It's been a tough couple of days for us here. It has been raining," she said, addressing the global audience. "We're fine. Thank you for your prayers," she dead-panned.

She then made fun of Jennifer Lawrence, who famously fell while walking up to the stage last year to collect her best actress Oscar -- and stumbled again as she arrived for Sunday's show.

"If you win tonight, I think we should bring you the Oscar," DeGeneres said.

While the best picture winner is difficult to forecast, other categories could be easier to predict.

Jared Leto fulfilled expectations by taking the first prize of the night, the best supporting actor Oscar for his heart-wrenching portrayal of a transgender woman suffering from AIDS in "Dallas Buyers Club."

Cate Blanchett is favorite for best actress for her turn in Woody Allen's "Blue Jasmine," while Matthew McConaughey is widely fancied for best actor for his role as homophobic HIV-positive AIDS activist Ron Woodroof in "Dallas Buyers Club."