Four British nationals have died while fighting for a rebel extremist group against the forces of president Bashar al-Assad in Syria, reports say.
Their deaths highlight the increasing international scale of the conflict, and come amid fears of the threat posed by extremists returning to the UK once their part in the war is over.
Security officials and experts say there is a real danger that the Islamists will look to pass on the skills and experience learned in Syria, radicalising and training up more recruits back in Britain.
Among the four British fighters killed in recent months was Mohammed el-Araj, 23, from Ladbroke Grove in West London, according to reports in The Times.
The newspaper said he died while his group in the al-Nusra front, a rebel force linked to al-Qa’ida, was attempting to ambush Assad’s troops in August.
He reportedly went by the name “Abu Khalid”, and appears armed with an AK-47 and dressed in rebel uniform in photographs taken in Syria.
Security concerns over what might happen if fighters like Araj survive the conflict and are allowed to re-enter the UK were raised last month when two men who had returned from Syria were arrested on suspicion of hatching a terrorist plot.
Raffaello Pantucci, of the Royal United Services Institute, told The Times that a growing number of deaths of British fighters in Syria could lead to an increased threat of a terrorist attack in Britain.
“The likelihood grows of someone deciding that they want to punish the West for standing by as the death and destruction in Syria continue, as does the risk that groups on the battlefield might decide to distinguish themselves by using these foreign recruits to launch attacks in the West,” he said.
Shiraz Maher, a senior fellow with the International Centre for the Study of Radicalisation at King’s College London, told the newspaper: “Many Britons have made it clear they intend to stay in Syria and seek martyrdom but they are young and angry and that motivation could mutate and one day they could return to attack the West.”
Meanwhile, a BBC Newsnight report heard from a Hampshire man who is fighting for the Islamic State in Iraq and the Levant (Isis) group, also linked to al-Qa’ida.
Ifthekar Jaman, 23, from Southsea, told the programme it was his “duty” to “try to establish the law of God” in Syria. “All these people are suffering. Muslims are being slaughtered,” he said.
The Foreign Office said it was looking into the Times report that four British nationals had been killed in recent weeks in the conflict.