The German equivalent of the FBI warned April 29 that a terrorist attack could occur within the next three weeks. Officials said they did not know of a specific target or date, but that U.S., Jewish and British sites were particularly threatened. The warning stated that an al Qaeda member in Germany had developed plans to take as many as 400 hostages from churches or cinemas in Germany, France and Britain and demand release of al Qaeda prisoners in exchange for the hostages or they would blow them all up. Three of the Sept. 11 suicide hijackers had once lived in Hamburg. Consider deferring visits to churches or cinemas for the next few weeks.