Il recente attentato al Museo ebraico di Bruxelles ha focalizzato l’attenzione degli apparati di sicurezza europei e nordamericani sulla pericolosità dei volontari jihadisti occidentali che combattono in Siria (stimati attorno ai 5.000) e che, rientrando in patria, potrebbero compiere attacchi.
Dal Financial Times di due giorni fa:

Western intelligence agencies have handed Turkish authorities the names of nearly 5,000 people they fear are attempting to travel to Syria to join al-Qaeda linked groups, in a stark illustration of the escalating terror threat posed by homegrown jihadis.
The number far exceeds the figure of 2,000-3,000 citizens already estimated to have travelled from Europe and the Americas to fight against President Bashar al-Assad. Security officials already fear the cohort could lay the groundwork for years of attempted terror attacks against the west on a level not seen since 9/11.
Counter-terrorism officials from EU countries and Turkey confirmed the size of the list to the Financial Times. An estimated 450 citizens have already travelled to Syria, alongside 700 from France and more than 300 from Germany. Turkey is the main transit point at issue.
The issue has jumped up the political agenda following three murders at a Belgian Jewish museum a fortnight ago, now believed to be the first instance of a “blowback” attack by jihadis returned from Syria.
“This is the top issue now in EU relations with Turkey,” said one EU official. “Each member state has a [terror] watchlist. All roads lead to the Turkish foreign ministry.”
Diplomats say Turkey has become much more responsive to their concerns in recent months, with Ankara this week designating one of the largest Syrian jihadi groups – Jabhat al-Nusra, al-Qaeda’s official affiliate – as a terrorist organisation.
Turkish officials say some but not all of Ankara’s western partners are now providing information on possible terror suspects.
Although Ukraine dominated headlines from the G7 summit in Brussels on Thursday, the primary security concern discussed was Syrian foreign fighters, according to security officials familiar with the talks.
Compiling a database of names of potential and current fighters has been one of the thorniest issues on which intelligence agencies – including many unused to working with each other – are trying to thrash out a solution.
In the UK, Whitehall security officials say there is now a recognition that it is an urgent pan-European problem due to the continent’s open border arrangements.
On Thursday, a group of nine European countries most affected by the threat held private talks in Brussels, security officials told the Financial Times. Senior ministers including UK Home Secretary Theresa May attended with their counterterror officials.
A Home Office spokesperson declined to comment on the details of the meeting.
Gilles de Kerchove, the EU’s top counter-terrorism official, confirmed that a group of some European countries was “working extremely closely together” to share information. “They have had meetings with Jordan, Morocco, Tunisia and Turkey,” he said. “For them it is Syria, Syria, Syria Syria.”
Mr de Kerchove told the Financial Times earlier this week that Europe should brace itself for more attacks.
US authorities have grown concerned too – and have been liaising closely with European intelligence agencies. Although only 70 Americans are thought to have gone to fight in Syria, visa-waiver programmes that allow Europeans from many countries to enter the US easily also make it vulnerable to “blowback” attacks.
The man charged with the Brussels attack of May 24 – in which two Israelis and a Frenchman died and a fourth victim was critically injured – was a French citizen who returned from Syria via Germany after travelling through Turkey and a series of stops in southeast Asia.
He was only eventually picked up – in Marseille – by chance as part of a routine customs operation, even though he was well known to authorities for his extremist views.
“They weren’t able to keep track of him,” said Richard Barrett, former director of global counterterrorism operations at the UK’s Secret Intelligence Service, better known as MI6. “A lot of the people who have gone to Syria no one has ever heard of. Some don’t even have criminal records. It’s going to be very hard to keep track of them.”
“And if we are talking about 3,000 people already, it only takes a small portion to succeed.”