When Keira Knightley threatened to kill co-star

London: Actress Keira Knightley reportedly threatened to kill her co-star Michael Fassbender if he touched her during a scene in A Dangerous Method.

The 26-year-old actress, who plays a Russian woman with severe psychological issues who comes between famed psychiatrists Carl Jung and Sigmund Freud, said she almost turned down the role because of a scene where her character, Sabine, is violently spanked, reported Daily Express online.

And Knightley warned Fassbender she would take revenge if one of the fake slaps actually struck her."I actually said to him before we shot the spanking scenes, 'If you touch me I will kill you' and he did remind me that I was tied to a bed at the time and really I shouldn't be making any threats," she said.

"The film is about so much more than S&M but (those scenes) weren't particularly easy. It's important to push yourself. I don't want to do the same thing again and again and again and I don't think people really want to watch that, and sometimes I'm going to fall flat on my face and I think I have done that, and will continue to do that but hopefully there will be some gems in there that are really interestingas well," Knightley added.