The masked jihadist known as “John the Beatle” has been identified by British security services, sources said Saturday.

MI5 and MI6 officials did not reveal the man’s name publicly, but senior British government sources confirmed they now know the identity of the ISIS extremist responsible for beheading American journalist James Foley, the London newspaper The Sunday Times reports.

The leading suspect in Foley’s murder is British rapper Abdel-Majed Abdel Bary – who traveled to Syria last year to fight in its civil war and recently tweeted a picture of himself holding up a severed head.

Bary joins a list of three other Brits who were identified as possible leaders of the jihadist group nicknamed by former hostages as “the Beatles.”

That list includes the brother of a British doctor once charged with kidnapping two Western war correspondents and a former gang member who converted to Islam before traveling to Syria to wage jihad.

It is now being estimated that up to 20 British extremists a month are heading to Syria and Iraq to take up arms with the ISIS, according to The Sunday Times.

“It is horrifying to think that the perpetrator of this heinous act could have been brought up in Britain,” British Foreign Secretary Phillip Hammond wrote in the Sunday Times.

In addition, Hammond referred to the actions of “John the Beatle” as “an utter betrayal” of everything the British stand for, The Sunday Times reported.

He added that Foley’s death would serve as a “reminder to us all that Islamic extremism in Iraq and Syria is not only causing huge suffering in those countries but is also a barbaric ideology threatening us at home.”

Foley will be honored in New Hampshire Sunday afternoon during a Mass of Remembrance held at Our Lady of the Holy Rosary in his hometown of Rochester.

Around 200 people gathered at a vigil Saturday night in Rochester to pay their respects and support the freelance reporter’s family.