Telephone hotlines and schemes to strip suspected militants of their passports are among eye-catching strategies to deter European fighters from joining Islamic State in Syria and Iraq.
But a more effective means - intelligence - is being under-utilised, according to diplomats and officials in Turkey, the main gateway from Europe to the militant’s self-proclaimed caliphate. Intelligence on recruiting networks is patchy and spy agencies are sometimes reluctant to share information, these officials say.
Thousands of foreigners from more than 80 nations including Turkey, Britain, parts of Europe, China and the United States have already joined the ranks of Islamic State and other radical groups in Syria and Iraq.
Many crossed via Turkey, flying into Istanbul or its Mediterranean resorts on Western passports, undetected among the millions of tourists arriving each month.
Turkish authorities have drawn up a “no-entry” list of 6,000 people, some as young as 14, based largely on intelligence from Western agencies, and have deported more than 500 suspected of seeking to join the extremists this year alone. But the list is far from comprehensive.
Some intelligence agencies are reluctant to fully share information with their Turkish counterparts, partly because Turkey does not share the same data protection standards and partly for fear of compromising the work of undercover agents seeking to infiltrate jihadist networks, security experts say.
“Data protection is an obstacle ... and this issue has put it under the spotlight,” said one European diplomat.