Terrorists operate with free reign in Belgium. The Belgian government has been inept when it comes to dealing with the threat of terrorism since its become the European hub for terrorists to plan and execute their operations from.
Update: The city centre of Brussels is being fenced off. Army and police are gathering outside several hotels and restaurants and streets have been closed, they are requesting people to not mention anything about the operation on twitter so their positions and movements won't be revealed, people have to stay away from the windows, something is going down