A left-wing extremist group claimed responsibility for the car-bomb slaying in Athens, Greece, of U.S. Navy Capt. William Nordeen and warned in a statement published Wednesday it would continue to strike at U.S targets until "the last American soldier leaves our country." The pro-Moscow evening newspaper Ethnos said the claim was made in a five-page statement found at the door of its editorial offices and was signed by the group November 17.