London: Intelligence agencies are hunting a new "Jihadi John" after an Islamic extremist with a British accent was shown directing the murders of five men accused of spying for the UK.
Latest IS video features child
Blast rocks Swedish apartment block
Samsung soars with AUS$9.3b earnings
Clinton: 'I accept your nomination'
Deep-sea camera catches mysterious purple blob
Greece, lenders clinch bailout deal
DNC: Clinton nukes Trump on security
Chelsea Clinton: Hillary is a 'protector'
Latest IS video features child
A young boy with a British accent and wearing army fatigues appears in the latest propaganda video in which five men are executed after 'confessing' to being British spies.
In a video released on social media on Sunday, the masked gunman warned David Cameron, the Prime Minister, that the West could never win in the war against Islamic State, while mocking the impact of RAF airstrikes.
At the end of the video a young boy aged around four, who seemed to speak with a British accent, also appeared on screen, threatening to kill non-Muslims.
The victims - who are said to have helped coalition forces by providing information about the whereabouts of IS suspects, including the group's deputy leader - were all shown being shot in the head at point-blank range after the British-sounding terrorist delivered his message of propaganda.
The ten-and-a-half minute video had echoes of those posted by the IS terrorist dubbed "Jihadi John", who was responsible for a string of murders including the beheading of British aid worker Alan Henning.
"Jihadi John", later identified as 27-year-old Mohamed Emwazi from London, was killed in a US drone strike last November.
MI5 agents were last night working to establish the identity of the new terrorist, amid concern that the video might signal the start of a new IS propaganda campaign, in the wake of the Britain's decision to join coalition airstrikes against IS targets in Syria.
A source in the Foreign Office said the propaganda video had likely been released to "divert attention away from IS's recent military failures in Iraq and its inability to look after the citizens in the areas it controls".
As well as speaking with a London-sounding accent, the terrorist made reference to the soldiers being paid the minimum wage, and labelled Tony Blair and Gordon Brown "arrogant and foolish" for the use of British troops in Iraq and Afghanistan.
The video began with apparent confessions from the five Arabic men who were wearing orange prisoner-style jumpsuits. The men claimed to have passed information to the West about prominent IS figures who were subsequently targeted by the coalition, including the group's deputy leader Abu Muslim al-Turkmani, who was killed in a US drone strike last August.
The video then cut to a desert area where the victims were shown kneeling before five gunmen clad in camouflage clothing and black masks.
Addressing his rant to Mr Cameron directly, the terrorist described him as a "slave of the White House" and "mule of the Jews".
Clutching a semi-automatic pistol he said Mr Cameron was an "imbecile" for thinking RAF airstrikes could have any impact. He said: "How strange it is that we find ourselves today hearing an insignificant leader like you challenge the might of the Islamic State.
"How strange it is that a leader of a small island threatens us with a handful of planes. One would have thought you would have learned the lessons of your pathetic master in Washington and his failed campaign against the Islamic State.
"But it seems that you, just like your predecessors Blair and Brown, are just as arrogant and foolish.
"In fact David, you are more of an imbecile. Only an imbecile would dare to wage war against a land where the law of Allah reigns supreme and where the people live under the justice and security of Sharia. Only an imbecile would dare to anger a people who love death the way you love your life."
Then, addressing a wider audience, the terrorist warned that one day Britain would be invaded with everyone forced to live under strict Sharia law.
He said: "All British government. All people of Britain, know that today your citizenship is under our feet and that the Islamic State, our country, is here to stay and we will continue to wage jihad, break borders and one day invade your land, when you will be ruled by Sharia.
"But those of you who wish to continue fighting under the banner of Cameron on the minimum wage, we say to you to ask yourself, do you really think your government will care about you when you come into our hands?
"Or will they abandon you as they have abandoned these spies and those who came before them, because you will lose this war as you lost in Iraq and Afghanistan.
"But this time when you lose your children will inherit your defeat and remember you as the fools who thought you could defeat the Islamic State."
After then shouting 'Allahu Akbar', Arabic for 'God is great', he then opened fire on the victim at his feet, shooting him in the back of the head.
The man slumped forward before the other gunmen all opened fire on their victims in a sickening killing spree. After a brief montage featuring IS propaganda slogans and music, the video cut to another desert landscape, where a young boy, thought to be aged around four or five, addresses the camera.
Wearing a camouflage top and a black IS headband, the youngster appeared to speak with a British accent as he pointed to the distance and said: "We will kill the kuffar (non-believers) over there" as he points to the distance.
While his accent was difficult to ascertain, the decision to use the child in the video suggested a determination by the IS propaganda machine to further shock and terrorise the West.