On the 11th anniversary of September 11, angry protesters climbed the walls of the U.S. Embassy in Cairo and hauled down its American flags, replacing them with black flags with Islamic emblems, CNN reports. The replacement flag read, "There is no God but Allah and Mohammed is his messenger," and protesters chanted anti-American slogans and held up bits of a shredded American flag to TV camera crews in front of the embassy. The incident prompted warning shots to be fired as a large crowd gathered outside, apparently upset about the production of a Dutch film thought to insult the prophet Mohammed, according to CNN producer Mohammed Fahmy, who was on the scene. An embassy operator said the facility had been cleared of diplomatic personnel ahead of the apparent threat, and Egyptian riot police were called to help secure the area. The U.S. Embassy said in a statement Tuesday that it "condemns the continuing efforts by misguided individuals to hurt the religious feelings of Muslims -- as we condemn efforts to offend believers of all religions."