Brad Pitt and Quentin Tarantino grabbed the spotlight Friday as the largest film festival in the Spanish-speaking world got underway.

The 57th edition of the San Sebastian film festival officially opened with a showing of Canadian director Atom Egoyan's psychological drama "Chloe" starring Liam Neeson and Julianne Moore, one of the 15 films in competition for the top Golden Shell award.

But it was a movie being shown out of competition, cult director Tarantino's "Inglourious Basterds", which took centre stage.

Pitt and Tarantino were to attend the Spanish premiere of the film, about a roving Jewish-American militia that kills and scalps Nazis in occupied France, and which was unveiled at the Cannes festival in May.

Hordes of fans braved foul weather in the northern Spanish coastal city to greet Pitt. Bearded and wearing a cap, leather jacket and large sunglasses, he signed autographs and posed for photographs as he arrived at his hotel.

He later addressed a press conference in which he spoke about his excitement in working with Tarantino.

"It was really fun, just really fun," he said. "When Tarantino is on set is energy. It's really difficult to sleep on set when Tarantino is on. The set is a church and he is God, you always learn something from God."

Organisers of the festival, which runs until September 26, have been forced to slash the budget this year, reducing the event by one day, due to cutbacks in public subsidies and from sponsors amid the economic crisis.

But they have vowed to maintain the quality, with films by a wide variety of top international directors.

"Chloe", which was applauded by the audience at its showing, mixes sensuality and eroticism.

It recounts the story of a doctor, played by Moore, who suspects her husband, a music professor played by Neeson, of cheating on her, and hires an irresistible young woman (Amanda Seyfried) to test his fidelity.

But the move gets out of hand and ends up putting her family in danger.

"The film is about marriage and the way we have to reinvent ourselves," Egoyan told a news conference. "It's about the role of fantasy and being able to hold them, and about the danger of fantasy."

He also spoke about the concerns and difficulties the cast and crew faced when Neeson's wife, British actress Natasha Richardson, was killed in a skiing accident during the shooting of the film.

"We were all concerned," by her death, he said. But "Liam is an amazing actor" and "we could finish the film" because he returned to the set.

On Saturday, the films vying for the Golden Shell continue when top French filmmaker Francois Ozon, who made "8 femmes" and "Swimming Pool", unveils his latest work "Le Refuge."

Last year's Golden Shell for best film went to Turkish director Yesim Ustaoglu's "Pandora's Box."