British intelligence agencies are probing the latest horrific ISIS [Daesh] execution video as speculation grows about the 'new Jihadi John'.
Horrifying footage of an Islamic State killer with an English accent threatening to attack the UK before gunning down five 'British spies' has been released by the group.
The video, released by ISIS's propaganda organisation, shows the masked man wielding a pistol as the four victims kneel in orange jumpsuits in the dust.
MI5 agents were reportedly probing the identity of the militant after he threatened David Cameron and British soldiers.
A Foreign Office source told the Telegraph the video may have been released to “divert attention away from Isil’s recent military failures in Iraq."
As many as 66 British people are believed to be in Syria or Iraq to join up with ISIS, according to the BBC.
There is unconfirmed speculation online the latest masked killer may be one of the Brits who have left their home country to join Daesh overseas.
Among those who have fled the country are Abu Rumaysah, one of a number of men arrested in September 2014 in an anti-terror operation and released on bail.
Rumaysah, also known as Siddhartha Dhar, was detained alongside radical hate preacher Anjem Choudhary on suspicion of supporting the banned extremist group al-Muhajiroun.
Police carried out raids on a number of addresses in London detaining 11 men.
Despite his arrest, it appears Rumaysah managed to flee the country and join jihadists.
Other men who have left the UK in recent years include brothers Nasser and Aseel Muthana, as well as their friend Reyaad Khan, all from Cardiff.
Former medical student Nasser appeared in a propaganda video for Islamic State in June 2014 with Khan.
The pair, both 20 when they fled for Syria, were later joined by Nasser's teenage brother, Aseel.
The brothers left behind their stunned family in the Welsh capital.
And a family of 12 from Luton went missing in July last year missing amid fears they travelled to Syria to join Islamic State.
The group flew to Bangladesh for a holiday in May but failed to return, and an ISIS representative issued a statement claiming to be on behalf of the family.
The latest ISIS video, which includes footage too graphic to be shown, has been condemned in Britain.
Labour MP Sadiq Khan said: "The evil and disgusting ISIS propaganda video shows why we need to do much more to tackle radicalisation in Britain."
A Foreign Office spokesman said: "We are aware of the video and are studying its contents."
By Sam Rkaina, Sam Webb, and Gareth Browne
Copyright © 2019 Trinity Mirror Group