In an interview concerning the prospect of moving terrorism suspects to Thomson Correctional Center in his northernwestern Illinois district, Manzullo said: "These are really, really mean people whose job it is to kill people, driven by some savage religion."
Those remarks were picked up by several blogs and news agencies.
An aide to Manzullo said he'd received about 20 complaints, according to Chicago Breaking News.
In his statement yesterday, Manzullo said he wasn't calling all of Islam a "savage religion," but rather was referring specifically to those devotees who practice violent, anti-modernist Wahhabism.
"Nevertheless," Manzullo said, "I apologize for any misunderstanding of my comments and I will endeavor in the future to clarify my remarks to make it absolutely clear that America is not opposed to Islam, but that we are fighting terrorists who believe in a savage, perverted, and violent form of Islam."