The race for the Oscars heats up this week at the Toronto International Film Festival, where a raft of films will focus on survival in dark times, with mounting political, religious and racial tensions around the world.

More than 300 feature and short films from 74 countries will be screened at the 42nd TIFF, the biggest film fest in North America, which opens Thursday and runs through September 17.

The event is often seen as a way for Oscar-conscious studios to generate buzz about their movies, with hundreds of filmmakers and actors to hit the red carpet in Canada's largest city.

Toronto is however facing increasing competition from other events for the best films and brightest stars.

"This year's big theme is survival," festival chief executive Piers Handling told AFP.

From climate change and overpopulation to terrorism, North Korea and fringe right-wing groups in America, Handling said, people worldwide are facing "an atmosphere of great uncertainty and a real fear about certain issues."

"I think it's a very unsettling time for many of us," he said, explaining that the films on offer would run the gamut of emotions.

"Some of the films are absolutely uplifting, showing that individually or collectively (you can overcome) if you harness your resources and work together. But of course, not all of the films have a happy ending," he said.

Handling highlighted "The Mountain Between Us," starring Idris Elba and Kate Winslet as two strangers fighting to stay alive after a plane crash in the wilderness, or "Stronger" about the 2013 Boston Marathon attack, starring Jake Gyllenhaal, as examples of films showing individuals trying to survive.

By contrast, American director Alexander Payne offers up a quirky solution to the issue of human consumption rapidly exhausting Earth's resources.

His science fiction social satire "Downsizing," about a man who chooses to shrink himself to simplify his life, stars Matt Damon.

Other featured films, meanwhile, chronicle efforts to live on in times of war and chaos.

Among those expected to generate buzz are the Winston Churchill biopic "Darkest Hour" starring Gary Oldman, Angelina Jolie's Cambodian genocide drama "First They Killed My Father" and "Kings," based on the 1992 Los Angeles race riots, starring Daniel Craig and Halle Berry.

- The contenders -

In past years, films such as "Spotlight," "12 Years a Slave," and "Slumdog Millionaire" went on from winning the Toronto festival's audience prize for best picture to take the top honor at the Oscars.

Last year, the musical "La La Land' won the prize and took home six Oscars including best actress and best director -- but not the top prize, despite the shocking mix-up with "Moonlight" at the end of the gala.

Many of the films being positioned for accolades this year will have already premiered at the Venice, New York or Telluride film festivals before they are screened in Toronto.

"The fall season is very crowded," Handling said, with the festivals all held within a short span of time.

They include "Battle of the Sexes" with Emma Stone and Steve Carell as tennis stars Billie Jean King and Bobby Riggs, "mother!" starring Jennifer Lawrence and George Clooney's Coen brothers-scripted "Suburbicon."

But Handling insists Toronto continues to be the launching pad for Oscar contenders.

"I think Toronto is still seen as the key place to amplify films going into awards season. Films may premiere in Venice or Telluride but the amplification actually happens here in Toronto," he said.

Notably among the hundreds of guests expected to grace the red carpet in Toronto are Clooney, Stone, Lawrence, Elba, Damon, Nicole Kidman, Jessica Chastain and Liam Neeson.

The festival will also host intimate talks with Jolie, Javier Bardem, Gael Garcia Bernal and Helen Mirren.

From the music world, rock legend Eric Clapton will be on hand for the premiere of the documentary "Eric Clapton: Life in 12 Bars," as will Eminem for his film "Bodied" about rap battling, and Drake, who produced a documentary about NBA star Vince Carter, who played for years in Canada.

Lady Gaga will perform following the screening of the documentary "Gaga: Five Foot Two."