Sharon Stone made her co-star's nose bleed while filming a violent scene for new movie Alpha Dog.

The actress plays a mother of a murdered teen in the film and decided that her character's aggression had to look realistic when she confronted one of her son's attackers, played by Ben Foster.

"I was trying to figure out how to hit him, because you have to hit a person when you're doing that kind of a scene," she explained. "You can't do those stunt hits because it doesn't really work in a scene like that.

"I was trying to hit him without hurting him but Ben just wouldn't let me because he knew the scene really required this kind of violence and this kind of aggression. It required me to really go for him.

"He forced me to aggress him and he forced me to hit him. He just kept pushing me and pushing me and I just lost it. He made me hit him until it broke my heart. It was so awful and his nose started to bleed."