The Islamic State (IS) militant group issued two videos warning that the "nightmare" of the Brussels terror attacks that killed over 30 people "had only just begun", Belgian broadcaster RTBF reported on Saturday.The videos were sent to Belgian newspaper Le Soir, showing two radical militants ordering western governments to withdraw their troops from Syria and Iraq."Tell them to withdraw their planes and soldiers and you will live in peace," a speaker said in one of the videos."The nightmare has only just begun. What will come later will be even more appalling," the video continued."Remember my message a year ago when it was announced that we would attack Paris and Brussels. We have achieved that and we have other targets," the video added. The city's Zaventem airport was the first target on Tuesday, with two suicide bomb explosions in the departures hall killing 11 people. An hour later, 20 people died in the suicide bombing at the Maalbeek metro station located in central Brussels.