David Cameron: James Foley Killing 'Barbaric'

David Cameron has condemned the "barbaric and brutal" murder of James Foley after holding crisis talks with intelligence officials.

The Prime Minister spoke after he was briefed in Downing Street by senior officials and the Foreign Secretary on investigations into video footage of the beheading of the US journalist by Islamic State (IS) extremists.

He said: "Let me condemn the barbaric and brutal act that has taken place and let's be clear what this act is - it is an act of murder, and murder without any justification.

"We have not identified the individual responsible, but from what we have seen it looks increasingly likely that it is a British citizen.

"This is deeply shocking. But we know that far too many British citizens have travelled to Iraq and travelled to Syria to take part in extremism and violence.

"And what we must do is redouble all all our efforts to stop people from going."

Mr Cameron said there would be no "knee jerk" escalation of British military involvement in the region and that the UK would stick to a "very clear foreign policy" of working with the new Iraqi government and helping arm the Kurds in their fight against the jihadists.

He added: "I have been very clear as Prime Minister over the past four years that this battle that we face against Islamist extremism - not the religion of Islam but a poisonous, extremist, violent narrative - is a generational struggle.

"It is a battle we have to fight in our own country, it is a battle with allies using everything that we have - our aid, our diplomacy, and yes on occasions our military powers - that we have to fight, whether it is dealing with this problem in Somalia, in Mali, in Afghanistan, in Iraq, in Syria, because as much as we want to focus on keeping ourselves safe here at home ... what happens in these other far-flung places can come back and cause huge harm here too."

The PM cut short a family break in Cornwall following the release footage appearing to show a masked man - speaking with a British accent - killing Mr Foley, who was seized by armed men in Syria in November 2012.

Scotland Yard, which leads counter-terror policing in the UK, has confirmed it is investigating the video and reminded social media users that spreading extremist material is a crime.

Shadow Foreign Secretary Douglas Alexander MP said: "The horrific footage of the killing of James Foley has shocked and outraged the world.

"Suggestions that the attack may have been carried out by a UK national are particularly concerning and the Government must now work with international partners to establish the facts and uncover any possible information about the perpetrator."

French President Francois Hollande said the crisis in Iraq represented the "most serious" international situation since 2001.

Meanwhile, UKIP leader Nigel Farage called on the Government to stop Britons who have gone to fight for IS from returning.