Well, I haven't been there since last October, I could be wrong.
Anyway, this breaks it down.
http://www.washingtonpost.com/wp-dyn/content/article/2005/11/16/AR2005111602519.html
There's a reason they call it the "Washington COM-post."
More of what I hear and read from people indicates that most insurgents are in fact foreigners. In fact, at one time, the percentage was all the way up to 90%.