Islamist extremists who have flocked to Syria to fight with groups linked to al-Qa'ida pose a direct threat to the UK because they will return to plot attacks at home, the British foreign secretary has warned.
William Hague said there was now "uncontested space" in Syria where Islamist groups were free to establish training camps that would equip and train foreign fighters, including British extremists.
"This is particularly concerning as we assess how some of the individuals being trained will seek to carry out attacks against Western interests in the region or in Western states now or in the future," he wrote in response to a question on how the conflict posed a threat to security.
Richard Ottaway, the Conservative chairman of the House of Commons foreign affairs select committee, said he believed the letter showed Mr Hague would declare that Britain was ready to intervene in Syria's civil war by arming rebels not under jihadist influence.
Experts said the assessment meant Syria was on a par with Somalia, Yemen and Afghanistan as a source of al-Qa'ida related plots targeting Britain.
"There is a large swathe of northern Syria where nobody is in control but local groups, including most notably the al-Qa'ida related Jabhat al-Nusra, are strong," said Dave Hartwell, a Middle East analyst.
UK officials have estimated that more than 100 British nationals or residents have gone to Syria to take part in the civil war. (© Daily Telegraph, London)