Venice, Aug 29 (IANS/AKI): Hollywood stars George Clooney and Sandra Bullock kicked off the Venice Film Festival with the world premiere of science-fiction thriller "Gravity".

In the movie by Mexican director Alfonso Curaon, 52-year-old Clooney and 49-year-old Bullock play two astronauts cast into deep space when a debris shower destroys their shuttle.

Clooney and Bullock Wednesday shared a few laughs together, waved to fans and posed for photographers after arriving in a water taxi.

Clooney, sporting a grey suit and and trademark shades, helped Bullock climb ashore. She wore a multicoloured Alex Perry dress with Giuseppe Zanotti stilletto sandals.

There are 20 movies contending for the top Golden Lion award at this year's festival, which will run till Sep 7. Director Bernardo Bertolucci will head the competition jury.

Special awards will be presented to Italian writer-director Ettore Scola, US director William Friedkin and Polish filmmaker Andrzej Wajda.