UK Special Forces conducting operations in Iraq have reportedly been handed a "kill or capture" list containing the names of roughly 200 British citizens accused of fighting alongside the Islamic State (Isis) terrorist organisation.
The elite UK military unit – which is routinely tasked with counter-terrorism, hostage rescue and covert reconnaissance missions – is believed to be acting under intelligence gathered by MI6, MI5 and GCHQ and in collaboration with the US Joint Special Operations Command.
Those captured in the operation will be handed directly to Iraqi authorities and may face execution under the nation's law if found guilty after a trial, the Sunday Times reported.
The news comes amid heightened military activity in the last Isis (Daesh) stronghold of Mosul.
A "senior defence source" told the Sunday Times: "A kill list has been drawn up containing the names of hundreds of very bad people. A lot of them are from the UK. The hunt is now on for British Islamists who have effectively gone off-grid.
"This is a multinational special forces operation. The SAS have their own part of the plan and they will be going after British nationals. This is a kill or capture mission and it has already begun. We do not have exact numbers of UK nationals in Iraq.
"The figures which have been in the press are just estimates. We know there are British people in Iraq, but we have no idea of their identities. That's the challenge we face. There is a lot of international co-operation because it's regarded as a global problem."
Referencing the 2015 terror attacks in Paris which killed 130 people and was claimed by IS, a source told The Sunday Times concerns were rising about a "backwash" from the ongoing situation in Iraq and Syria and that it represents an "urban terrorist threat to the UK".
As SAS operations in the region are secret, the UK Ministry of Defence (MoD) has declined to comment on the military activity. However, sources told the Sunday Times that regular soldiers in Iraq to help train Iraqi troops did not have powers to detain IS fighters.
The news comes after British troops were recently given the green light to continue training Syrian moderate opposition forces.
As reported, on 25 October defence secretary Michael Fallon announced that at least 20 soldiers will be deployed to "to provide vetted members of the moderate Syrian opposition with the skills they need to continue to take the fight to Islamic State".