UK Syria fighters: Criticism and sympathy for Cardiff trio
25 June 2014 Last updated at 08:01 BST
Home Secretary Theresa May says people who have travelled from the UK to fight in Syria could pose a real danger when they return.
She made her comments while giving a lecture at London's Mansion House on Tuesday night and follows on from a chilling online film posted last week promoting the terror group Isis and preaching Sharia law.
It featured two men from Cardiff - Nasser Muthana, 20 and friend Reyaad Khan. Nasser's younger brother, 17-year-old Aseel is also believed to be out in Syria.
Reporter Mark Hutchings has been out in Butetown in Cardiff, where the Muthana brothers live. He found criticism of what they did, but some sympathy for why they did it.