US air strikes against Islamic State extremists in Iraq continued as intelligence agencies on both sides of the Atlantic worked to identify the British jihadist believed to have carried out the brutal murder of American journalist James Foley.
Analysts were sifting through the available evidence for clues amid suggestions that the Islamic State extremist is from London.
The jihadist, referred to in the video as John, is reported to be the ringleader of a trio of UK-born extremists nicknamed after members of The Beatles responsible for guarding Western hostages, with the two others dubbed Paul and Ringo according to the BBC.
In the video of the murder of Mr Foley, US president Barack Obama was warned that the life of American hostage Steven Sotloff hinged on his "next decision".
But the US continued to launch air attacks on Islamic State (IS) forces to shore up Kurdish and Iraqi efforts to hold the strategically important Mosul Dam.
British spies are heavily involved in efforts to identify Mr Foley's killer and his group of extremists, with the Cheltenham-based eavesdropping agency GCHQ playing a vital role in intercepting any electronic communications between jihadists in Syria and Iraq.
The British agencies – MI5, MI6 and GCHQ – were also working with US and European counterparts and receiving reports from agents on the ground to try and build a more complete picture of the scenario in Iraq and Syria.
Hundreds of Britons who have travelled overseas to take up jihad have for some time been of central concern to the security services.
British prime minister David Cameron, who returned to Cornwall on holiday after interrupting his break to take charge of the British response to the release of the murder video, said "far too many" Britons had travelled to the region to take part in jihad.
Foreign secretary Philip Hammond said "significant numbers" of British nationals had been "involved in terrible crimes, probably in the commission of atrocities" with the Islamic State (formerly known as Isis) and other extremist groups.
Downing Street said the prime minister would continue to receive regular updates and briefings on the situation while he was in Cornwall.
Murder
A No 10 spokesman said: “The prime minister has returned to Cornwall after holding meetings in Downing Street yesterday on Iraq and Syria, following the murder of James Foley. He remains in close contact with his team and will be kept fully up to date.”
Dr Andrew Mumford, a lecturer in politics and international relations at Nottingham University, said intelligence services faced a “big task” in trying to identify the murderer, and would be combing through people known to have links with Britons who have travelled to fight in Syria.
But he warned the agencies could face problems if the killer had travelled to the region “under the radar” with “no background in terrorism or any other criminal activities”.
On the role of “The Beatles” in guarding kidnapped Westerners, he said: “A picture is emerging that IS is now explicitly using Western jihadists to take control and look after Western hostages. That is an important and interesting development.”
An attempt by US special forces this summer was launched in an attempt to rescue hostages including Mr Foley, senior officials in the Obama administration said yesterday. The mission was authorised after intelligence agencies believed they had identified the location where the hostages were being held.
Firefight
But several dozen special operations troops who were dropped by aircraft into Syria did not find them and engaged in a firefight with IS militants before departing. The officials said a number of militants, but no Americans, were killed. One American suffered a minor injury when an aircraft was hit.
The murdered journalist’s younger brother Michael criticised the US government, saying he thought it could have done more to save him.
One of the agencies Mr Foley worked for, GlobalPost, has said IS threatened to execute him a week ago and that the US authorities were informed.
The film shows Mr Foley (40) who worked for organisations including Agence France-Presse and went missing in Syria in 2012, kneeling in a desert-like environment at an unknown location as an IS fighter stands by his side dressed in black and with his face covered.
Speaking with an apparently English accent, the killer accused America of “aggression towards the Islamic state”, adding: “You have plotted against us and gone far out of your way to find reasons to interfere in our affairs.” (-PA)