I was watching CNN Inside Politics a few minutes ago when Wolf Blitzer came on with a breaking story.
Apparently, three separate high-level sources have confirmed to CNN that Shia militants associated with al-Sadr have launched what was described as "a major offensive," fighting against Marines, with as-yet unspecified casualties, in the city of ar-Ramadi. This is about 80 miles or so west of Baghdad, as best as I can tell from my atlas, and no more than 40 miles west of Fallujah.
A couple of things to bear in mind:
CNN has been known to overhype "breaking news" - remember that college girl who apparently faked her kidnapping a few days ago? And this story comes with absolutely no on-the-ground reporting, much less video or audio, only what's been claimed by sources in Washington.
On the other hand, cable news in general lives for dramatic graphics - they're probably less likely to overhype a story when there's no cool video. And certainly there's no reason for the Bush crowd to overhype a story about all hell breaking loose in Iraq.
Also, Iraq is just about 12 hours different from the US West Coast, so this is the wee hours of the morning over there - whatever is going on, it probably isn't just a few hundred young men runing around in the streets firing pistols. As said above, Blitzer said it was being characterized as a major offensive.
Finally, the location of ar-Ramadi - pretty close to Fallujah - sounds like some kind of coordination with, or at any rate support for, the Sunni militants in Fallujah. Which in itself adds a whole new level of possible seriousness.
Anyway, that's what was reported half an hour ago. I'll see what Wolf has at the top of the hour, but this is a heads-up.