France on Monday set up a crisis cell on the eve of a deadline set by the shadowy AZF group, which in March threatened train bombings - a new "Madrid tragedy" - if Paris did not fulfil its demands for money. "Do not compromise your fellow citizens' security," it said in a letter sent on March 15 to both French President Jacques Chirac and the interior ministry. "From May 3, we will again be in contact with you," the group - or individual - wrote, adding that it expected a response to its eventual demands "within a short period of time". The March letters bore a different logo but used the same code name as a group that first appeared in December 2003, threatening to blow up French railway lines unless it was paid millions of euros in cash. The February 2004 discovery of a sophisticated bomb hidden under stones on a train line between Paris and Toulouse underlined the seriousness of the initial AZF threat. Police and the first group of blackmailers communicated via classified ads in the daily press, lending a veneer of intrigue to the case, which was only heightened with the failure of a complex ransom drop in March 2004.