Director George Lucas has warned that the final Star Wars movie is not suitable for young children.

Lucas has described Episode III - Revenge Of The Sith as "dark and violent", adding that he expects it to be given an over-13 rating in the US.

"I don't think I would take a five year old to this, it's too strong," Lucas explained.

"The film is more dark, more emotional. It's much more of a tragedy. I'm very pleased with the whole thing."

The movie is released on May 19.