The group which says it was behind the hoax bombing of a Paris department store is causing consternation in France. The so-called Afghan Revolutionary Front claims it planted five sticks of dynamite in Le Printemps. But the explosive device found by police had no detonator, and the text of a letter apparently sent by the group to a French news agency, warning France to pull its troops out of Afghanistan, did not match the normal threats given by Islamic terrorist groups.International terrorism expert, Jean-Charles Brisard, said: “Usually, firstly, the threats are not virtual. In this case the explosive device was very simple. There was no trigger. There was no detonator, and also the text of the claim had no reference to any jihadist language or Islamic language.” But police took the letter seriously, evacuating the department store. Half a kilogramme of dynamite was found by sniffer dogs in a toilet cistern. Security has now been stepped up across France and the government will meet for crisis talks later today.