Europeans 'radicalised in Syria'
24 April 2013 Last updated at 08:06 BST
The EU's head of counter-terrorism has told the BBC that hundreds of Europeans are now fighting with rebel forces in Syria.
Intelligence agencies are concerned some could join Jihadist groups linked to Al Qaeda and later return to Europe to launch terrorist attacks.
The BBC has met one Belgian family who say their son has travelled to Syria to fight alongside rebels against Bashar al-Assad's regime.
Europe correspondent Duncan Crawford reports.
First broadcast on BBC Radio 4's Today programme on Wednesday 24 April 2013.