One neighbourhood in western Brussels has become the focus of attention for European security services in the wake of the Paris attack.
It has emerged that the suburb of Molenbeek served as a planning and logistics base for the jihadis.
Molenbeek is also the area where other terrorists who carried out recent attacks in France and Belgium found a haven and acquired weapons.
A series of police raids took place in the suburb this week, where it is estimated that at least a third of the 100,000 residents are Muslims of Moroccan and Turkish origin.
Salah Abdeslam, one of the suspected Paris attackers - who is still at large - lived in the neighbourhood, along with his brother Ibrahim, who was killed in the attack when he exploded the suicide-vest he was wearing.
Another Daesh member who lived in the area is Abdelhamid Abaaoud, the man intelligence services believe directed the attack from Daesh's Syrian stronghold in Raqqa. Around 300 Belgian citizens are currently believed to be fighting with Daesh in Syria, the highest proportion of any European country. In addition, French terrorists Mohammed Merah, who killed four Jews and three soldiers in Toulouse in 2012; Mehdi Nemmouche, who murdered four people at the Jewish Museum in Brussels last year; and Amed Coulibaly, who killed four Jews in the Hyper Cacher grocery in Paris in January, are all known to have visited Molenbeek and received assistance there.
Locals say that one of the main factors leading to radicalisation is a growing generational divide between parents who emigrated to Belgium and worked hard to build a future for their families, and the sons who were born in Brussels and do not feel part of the society their parents hoped they would join.
The clannish atmosphere in the neighbourhood and other areas of Brussels with large Muslim immigrant communities is exacerbated by the local government system.
The current set-up, which splits powers between a host of mayoralties and councils, makes dealing with alienation and radicalisation in a systematic fashion much more difficult.
For terrorists planning attacks in other European countries, an area like Molenbeek is not just a friendly base, it is also a way of placing bureaucratic obstacles in the way of the intelligence services pursuing them.
Jean-Louis Bruguière, the former senior investigating judge in charge of counter-terrorism in France, says: "When the attackers use a different country to plan and prepare, it makes it very complicated for us to detect them. And even if we are very close to that country and share intelligence, as we do with Belgium, it's not the same. Each member-state of the EU has their own agenda and sense of priorities and understanding of the intelligence."
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