Beyonce Knowles beat up her co-star Ali Larter in her new film.

The star plays a woman who has to defend her family from a crazed stalker, played by Larter, in new movie "Obsession" and she didn't hold back when the two actresses had to brawl.

Larter said: "Our fight scene was so fun! I'm glad it looked scary. We went all the way to make sure it looked real. I was bruised all over, scraped up. That's the fun of it! Neither of us are girls who phone things in."

In order to get into character, Knowles has revealed she drew inspiration from her nephew Daniel, her sister Solange's four-year-old son.

She said: "To prepare, I tried to tap into things that are available to a lot of people. I thought about my sister and what it would be like if someone were threatening her child. I used my life experiences and my nephew to get my mind right."