Ralph Fiennes and Rachel Weisz star in The Constant Gardener

The new release from Brazilian director Fernando Meirelles, who made the Oscar nominated City Of God, also stars Bill Nighy and Danny Huston.

George Clooney's second outing as a director, Good Night And Good Luck, will close the festival on 3 November.

His film is in the running for Venice's Golden Lion award.

Personal loss

It is also the curtain-opener for the New York Film Festival, which gets under way next month.

The film chronicles the real-life conflict between Senator Joseph McCarthy and television newsman Edward R Murrow in 1950s America.

The Constant Gardener is based on the best-selling novel by John Le Carre, and tells the story of one man's quest to uncover the truth behind a personal loss and a far more wide-ranging conspiracy.

This year's festival is due to screen 280 films from 60 countries.