AN INTERNATIONAL manhunt has been launched for a suspected British jihadist believed to have carried out the videoed beheading of US journalist James Foley.

Spooks yesterday began sifting through the footage for clues amid growing evidence that the black-clad Islamic State (Isis) extremist — identified by a former hostage as “John” — is from London.

It comes after Prime Minister David Cameron confirmed that it is “increasingly likely” that the killer was a British citizen.

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

In the video posted by IS, a masked militant attacks US “aggression towards the Islamic State” in an apparently London accent before beheading Mr Foley. 

A former hostage of the group told the Guardian the executioner was a “Londoner” who leads a team of three British extremists known as “the Beatles.”

Mr Cameron and US President Barack Obama have pledged to continue to fight the extremists — despite a new threat to kill captured US journalist Steven Sotloff.

Mr Foley was murdered after being abducted by IS in north-west Syria on November 22 2012. 

National Union of Journalists general secretary Michelle Stanistreet described the incident as “deeply shocking.”

She warned Mr Foley is among dozens of journalists who have lost their lives reporting in the “lethal climate” of the Middle East, Ukraine and Africa this year. 

“It is deeply alarming to see that journalists are becoming direct targets and their lives are being put at risk,” she said.