Canadian Rachel McAdams plays Christine, a domineering and manipulative manager in a successful advertising firm who is both attracted to and threatened by her talented colleague Isabelle, portrayed by Sweden's Noomi Rapace.

When Christine steals an idea from Isabelle to further her career their friendship begins to unravel, hastened by Isabelle's decision to start an affair with her rival's boyfriend.

Rapace said some of the steamier scenes she shared with McAdams were improvised.

"I think it was something that we talked about and kind of discovered and tried out on the day rather than something that was written on the page," she told reporters after a press screening and ahead of the red carpet world premiere on Friday.

"We did different takes and some of them were kind of a little bit more sexual ... and some were kind of colder because I think those two women, they use sex as a weapon.

"They are not in love and they are not really attracted to each other but it's one of the tools they use against each other and against people around them."

De Palma, best known for films including "Carrie", "Scarface", "The Untouchables" and "Mission: Impossible", said he had been taken aback by some of the acting.

"They surprised me quite a lot, because they pushed the material in all kinds of different directions," he told Reuters Television in an interview.

He added that he made Passion principally for women.

"This is a movie for women, about women," said the 71-year-old. "It's for women and it's very interesting to see how women will react to it.

"They (the characters) are beautiful women, they are manipulative women, they are sexy women and I'm very interested in a woman's reaction. The movie is not too violent because women don't like violent movies but it's scary and it's surprising."

Although De Palma said he believed Passion had a chance of winning the Golden Lion for best picture in Venice, jeers after a press screening and negative early reviews suggested he was at best an outsider for the coveted prize announced on Saturday.

"The impression is that De Palma is indulging himself with homages to his own Hitchcockian greatest hits, with results that veer close to self-parody on occasion and emphasize just how far this once-outstanding director's creative star has plummeted," wrote Neil Young in The Hollywood Reporter.

Passion is based on a 2010 French movie "Love Crime", and is set in Berlin. He said he always saw the potential of setting movies outside the United States.

"I'm the guy that thought up, 'well, may be we should do Mission: Impossible all over the world'," he told the press briefing.

"It was originally written to be done in the (American) Midwest and I said, 'but there is a lot of fantastic looking places all over the world plus there are all these fantastically great stars in each country. Why don't we do it that way?"

Passion next screens at the Toronto film festival, and has a theatrical release date in some European countries in February.

(Reporting by Mike Collett-White, editing by Paul Casciato)

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