Julia Roberts and Ewan McGregor shoot intense scenes for their upcoming film August: Osage County in Bartlesville, Oklahoma.

The world premiere of The Fifth Estate, a ripped-from-the-headlines drama about Julian Assange and the creation of WikiLeaks, will open the 38th Toronto International Film Festival, which typically yields a number of Oscar contenders.

Widely considered the kick-off to Oscar season, the 2013 festival will feature films starring Meryl Streep, Idris Elba, Colin Firth, Chiwetel Ejiofor, George Clooney and others, organisers said on Tuesday. The 11-day event opens on September 5.

Elba takes on the lead role in Mandela: Long Walk to Freedom, a dramatisation of the life of legendary anti-apartheid South African leader Nelson Mandela, who has been hospitalised with a lung infection for the last six weeks.

The Fifth Estate, directed by Bill Condon, stars Benedict Cumberbatch as Assange, the founder of anti-secrecy website WikiLeaks.

This marks the third straight year the festival has opened with a high-profile title, after years of using the opening slot to highlight smaller Canadian films.

“As soon as we saw it, we knew that it would set the right tone for opening night. It’s a movie about what we thought is one of the most important issues of the day – information and who controls it,” said Cameron Bailey, the festival’s artistic director.

In addition to his turn as Assange, Cumberbatch also stars in August: Osage County, a star-studded family drama set in Oklahoma that also features Julia Roberts, Meryl Streep, Ewan McGregor, Abigail Breslin and Chris Cooper.

Gravity, a thriller set in space starring George Clooney and Sandra Bullock, will be screened at the festival. Gravity is director Alfonso Cuaron’s first feature film since Children of Men in 2006.

Arrested Development actor Jason Bateman will make his directorial debut with Bad Words, a comedy in which he stars as a 40-year-old who enters a national spelling competition and dominates his prepubescent challengers.

Blue is the Warmest Colour, the lesbian love story that won the Palme d’Or for best film at the Cannes Film Festival, will have its North American debut at the festival.

One Chance, the film about the first-ever Britain’s Got Talent winner Paul Potts, starring James Corden, Julie Walters and Mackenzie Crook, will also be screened for the first time.

Other world premieres include romantic comedy The Love Punch starring Emma Thompson and Pierce Brosnan, director Richard Ayoade’s new film The Double, with Jesse Eisenberg and Mia Wasikowska and crime thriller Dom Hemingway starring Jude Law and Richard E Grant.

Launched in 1976, Toronto’s film festival ranks among the world’s top movie events and often serves as a launch pad for international films seeking North American distribution

The Invisible Woman, the story of Charles Dickens’s mistress Nelly Ternan, directed by and starring Ralph Fiennes, with Felicity Jones as Ternan, will also make its world debut at the festival.

Other films screening at the festival include Kill Your Darlings, featuring Harry Potter star Daniel Radcliffe as Beat poet Allen Ginsberg, and political comedy The Grand Seduction, starring Brendan Gleeson and Taylor Kitsch.

The 38th Toronto Film Festival will close on September 15 with the premiere of Life of Crime, based on Elmore Leonard’s novel The Switch, with an all-star cast includ-ing Jennifer Aniston, John Hawkes, Mos Def, Isla Fisher and Tim Robbins.

Launched in 1976, Toronto’s film festival ranks among the world’s top movie events and often serves as a launch pad for international films seeking North American distribution.

The Toronto festival has a solid track record of unearthing films that go on to succeed at the Academy Awards, such as Slumdog Millionaire and The King’s Speech, which won best film Oscars. Last year’s winner of the People’s Choice award, the festival’s top prize, was Silver Linings Playbook, an Oscar nominee for best picture.

Last year, the event screened 372 features and short films.