A U-S-born Yemeni cleric, Anwar al-Awlaki, posted a video message on radical web sites today calling for the killing of Americans.He said Americans are from the �party of devils,� and no special religious permission is required to kill them. US investigators say al-Awlaki’s sermons may have inspired the man who tried to bomb an airplane over Detroit on Christmas day and the Army psychiatrist who shot 13 people in Fort Hood, Texas. The Christian science monitor correspondent Laura Kasinof reports from Sana’a.