The FBI has announced charges against two suspected British terrorists accused of being part of a "notoriously brutal" Islamic State cell known as "The Beatles".

Alexanda Kotey and El Shafee Elsheikh, both in their 30s and from west London, allegedly belonged to the cell of executioners in Syria - known as "The Beatles" because of their British accents.

John Demers, assistant attorney general for national security, announced the charges during a news conference in the US on Wednesday.

He said: "The defendants are charged with terrorism offences related to hostage-taking and killing of four Americans, as well as citizens of Great Britain and Japan."

Two alleged Islamic State militants known as the ‘Beatles’ will arrive in the United States on Wednesday to face trial on U.S. criminal charges for their alleged involvement in beheadings of American hostages in Syria, the Department of Justice said https://t.co/Nt7smFiCjp pic.twitter.com/BpEDOji4Gj

— Reuters Legal (@ReutersLegal) October 7, 2020

Mr Demers added that he was "pleased" to confirm Kotey and Elsheikh are in FBI custody and are due to appear in federal court in the Eastern District of Virginia.

The pair will now come before the court to "face justice for the depraved acts alleged against them in the indictment", he added.

If convicted, they face life in prison.

Kotey and Elsheikh are said to be responsible for the deaths of a number of Western captives, including Britons Alan Henning and David Haines.

Mr Haines' brother Mike told Sky News: "The Haines family along with all the families of the victims are pleased to see this step forward in the judicial system."

The pair are also accused of killing American journalists James Foley and Steven Sotloff, and aid workers Kayla Mueller and Peter Kassig. Their families welcomed the charges.

"Now our families can pursue accountability for these crimes against our children in a US court," they said in a statement.

James Foley's mother Diane told Sky News: "This feels miraculous in many ways and its thanks to the US government, the UK government and countless other pro bono attorneys and non-profits who have supported us and given us strength as families to pursue this first step in justice.

"It's hugely important. At times I despaired it would ever happen.

"Hopefully these men will implicate others and give us information about where the remains of our children are."

She said the trial would be "difficult" but said it was time for the world to know what "Jim and the others went through".

Secretary of State Mike Pompeo tweeted: "We welcome the transfer of the ISIS 'Beatles' to the United States to stand trial in a court of law.

"The United States will not rest until these alleged terrorists are held accountable for their crimes and justice is delivered to their victims' families."

The IS militant group is known for beheadings and the barbaric treatment of aid workers, journalists and other hostages in Syria.

Many of these executions were filmed and broadcast around the world in graphic detail.

The pair were captured by the Syrian Democratic Forces in January 2018 and transferred to the custody of the US military in Iraq in October 2019, remaining there ever since.

Mr Haines, a 44-year-old former aircraft engineer and humanitarian from Perth in Scotland, was beheaded in Syria in 2014 after being held prisoner for 18 months.

Mr Henning, a 47-year-old aid worker from Lancashire, was also beheaded in 2014 after being captured by extremists in Syria.

Kotey and Elsheikh were captured by the Syrian Democratic Forces in January 2018 and transferred to the custody of the US military in Iraq in October 2019, remaining in American custody ever since.

The cell's ringleader was said to have been Mohammed Emwazi, known as Jihadi John, who was killed in a US airstrike in 2015.

The group's fourth member, Aine Davis, was later jailed in Turkey.

US attorney general William P. Barr said: "These charges are the product of many years of hard work in pursuit of justice for our citizens slain by ISIS.

"Although we cannot bring them back, we can and will seek justice for them, their families, and for all Americans.

"Our message to other terrorists around the world is this - if you harm Americans, you will face American arms on the battlefield or American law in our courtrooms.

"Either way, you will be pursued to the ends of the earth until justice is done."

Mr Demers was asked to confirm that the US was sticking to its decision not to seek the death penalty for the pair.

"I think the attorney general made that very clear in his letters to the home secretary, that he decided on balance that we were not going to be pursuing the death penalty in this case and that's where we are," he added.

In August, Mr Barr made the commitment to make it easier for the UK courts to allow the British authorities to share information with prosecutors in the States.

G. Zachary Terwilliger, the US attorney for the Eastern District of Virginia, said: "These alleged terrorists both grew up in the United Kingdom where they became radicalised.

"Their role within the ISIS terrorist organisation was that of being part of a brutal hostage-taking scheme by which American, European and Asian citizens were taken hostage from approximately 2012 to 2015."

He said "their vicious acts and those of co-conspirators" are alleged to include forced witnessing of murders, mock executions, shocks via Taser and beatings - among other brutal acts.

Mr Demers was asked how important getting the British evidence for the case was, as a High Court ruling last month allowed the UK to share case information with US authorities.

He told reporters: "We decided that if we were going to do this case, we were going to tell the fullest story we could of what these defendants did and we were going to put on the strongest case possible.

"And with the British evidence I think we can do that very well."