Who Is 'Briton' Who Beheaded James Foley?

Counter-terrorism police in the UK say they are investigating the British-accented Islamic State fighter who beheaded journalist James Foley.

In a video posted by the militant group to social media sites, the man speaks in English as he says US airstrikes are to blame for the killing of the 40-year-old American.

The killer, who is clad in black and covers his face during the video, appears to have a London accent, appears to be left-handed and is of average height.

The Metropolitan Police Service Counter Terrorism Command said it was investigating the contents of the video.

James Foley was made to read out a statement before he was killed

It added: "We would like to remind the public that viewing, downloading or disseminating extremist material within the UK may constitute an offence under Terrorism legislation."

At least 400 people are known to have travelled from the UK to Syria and Iraq to fight for Islamic State (IS) - formerly known as Islamic State in Iraq and Syria (ISIS).

Concerns have been raised that radicalised young men from Western countries will return to their home nations and could be used to carry out attacks.

Sky's Middle East Correspondent Sherine Tadros said: "We know that around 400 British nationals have joined IS, probably more than that in the last few months as their recruitment has gone into overdrive.

Brighton student Abdullah Deghayes, 18, killed in Syria

Abdullah Deghayes was killed while fighting in Syria in May

"Now they are being used in these more serious videos to try to pressure foreign governments - and also people in these countries - to try to pressure their governments not to intervene."

Security agencies, including the FBI and MI5, will be tracking those who have travelled to Iraq and Syria to join the militant organisation.

A Home Office spokesperson added: "The police and security services are actively working to detect and disrupt terrorist threats.

"People seeking to travel to engage in terrorist activity in Syria or Iraq should be in no doubt we will take the strongest possible action to protect our national security, including prosecuting those who break the law.

"We also have a wide range of powers at our disposal to disrupt travel and manage the risk posed by returnees."

Nasser Muthana, centre, has been disowned by his father

Radicalisation expert Shiraz Maher told Sky News that Britons were at the "forefront" of the IS conflict and were "not taking a back seat" in the violence.

Crawley father-of-three Abdul Waheed Majeed, 41, became the first Briton suspected of staging a suicide bomb attack when he attacked a jail in Aleppo in February.

In May, 18-year-old Abdullah Deghayes, from Brighton, was killed while fighting in Syria alongside his two brothers Jafar and Amer.

In June, Cardiff students Nasser Muthana and Reyaad Khan - both 20 - appeared alongside Abdul Raqib Amin, from Aberdeen, in an IS recruitment video urging Westerners to join the fighting.

Amin, 26, was reportedly killed in a gun battle near Ramadi in July, while Ahmed Muthana said he had disowned his two sons, Nasser and Aseel, when they joined IS.

And earlier this month, 25-year-old former Primark supervisor Muhammad Hamidur Rahman, from Portsmouth, was reportedly killed while fighting for IS in Syria.

Foreign Secretary Philip Hammond said authorities were closely monitoring those attempting to join IS.

He said: "We have a substantial programme here in the UK which seeks to intercept people who are at risk of being attracted by extremist ideologies.

"We have powers to withdraw passports from people we believe are likely to go and join extremist organisations and commit violence abroad.

"And of course we have powers to arrest them and prosecute them on their return."