whenever there is an attack against u.s. forces or iraqi "collaborators" in iraq, the u.s. immediately blames saddam loyalist, or foreign fighters. i've never heard them give much evidence for either theory, but inevitably every incident is attributed to one or the other, but never any non-baathist iraqis. any home-grown resistance to the occupation is a story the administration does not want told.
in the last 24 hours there have been a whole series of attacks in iraq, beginning with an attack on the al-rashid hotel (possibly an attempt to assassinate deputy defense secretary paul wolfowitz). like always, who is behind it is not clear, but that does not stop the military from stating with certainty who it is:
for example brigadier general martin e. dempsey said "We have a very good idea of who's attacking us in Baghdad." Although the General "did not provide any details" to the new york times reporter in the article behind that link "he largely ruled out foreign terrorists." dempsey said "We have not seen any infusion of foreign fighters in Baghdad." dempsey also called the mechanism that fired the rockets at the hotel a "'Rube Goldberg device' and that its crudeness indicated the weakness of the forces opposing U.S. occupation"
on the other hand brigadier general mark hertling says that all of the bombings were done by foreign fighters: "There are indications that certainly these attacks seem to have been the operations of foreign fighters. They are not something that we have seen in the former regime loyalists." hertling added that the attacks were "amateurish."
so to summarize: foreign fighters are behind the attacks even though they have also been ruled out. instead, the responsible party is probably loyalist of the former regime, except that this is not something that they are likely to have done. the only thing there is broad consensus about is that the attacks (the most effective so far in terms of casualty count) are "crude" or "amateurish." but as billmon points out, this is nothing more than "the arrogance of the rich, transferred to the battlefield."