A former head of counter-terrorism at MI6 has told Sky News up to 300 Islamist fighters from Iraq and Syria may have returned to the UK and could be planning to carry out attacks.
Richard Barrett gave the warning after footage emerged online apparently showing several young British jihadists in Syria in a recruitment video for the extremist militant group ISIS.
In the footage they urged UK Muslims to join insurgents there and in Iraq.
Two have been identified as Cardiff brothers Nasser Muthana, 20, and 17-year-old Aseel Muthana
Sky News understands two Cardiff men who travelled to the Middle East with Nasser Muthana were arrested by police on suspicion of receiving terrorist training and attending a place used for terrorist training.
The arrests were made in March and April this year when the men returned to the UK. The pair, aged 19 and 23, were later released without charge.
Mr Barrett, who spent more than a decade tracking the Taliban in Afghanistan, told Sky News the hundreds of Britons possibly heading back to Britain was an “absolute nightmare” for security services.
He added they did not have the resources to be able to look at all of them.
“So they have to prioritise which will be difficult. Some of them will have come to the attention before they went to Iraq and so maybe they will be at the top of the list.
“But others are probably completely unknown and may be even their return is unknown and will only come to light later.
“It doesn’t take a big percentage of 300 people to cause an enormous problem so I think the security services are extremely concerned about this.”
On Saturday, it emerged around 500 people from Britain have joined the ISIS ranks making the job of tracking them a hugely difficult task.
Meanwhile in Iraq, Sunni militants have captured four more towns in western Iraq, according to Sky sources.
Led by ISIS, they took moved from the al-Qaim border crossing they seized on Saturday to take Haditha, Anah, Rotba and Rawa on the road to Ramadi.
Iraqi government forces reportedly put down their weapons and fled as the militants arrived
Sky
