Two members of the notorious Islamic State kidnapping cell dubbed the "Beatles" pleaded not guilty in a US court on Friday to charges of conspiring to murder four American hostages.

El Shafee Elsheikh, 32, and Alexanda Kotey, 36, were flown to the US from Iraq on Wednesday to face trial for involvement in the murders of American journalists James Foley and Steven Sotloff and relief workers Peter Kassig and Kayla Mueller.

Appearing from prison by videolink, they pleaded not guilty during a hearing in US District Court in Alexandria, Virginia before Judge TS Ellis and waived their right to a speedy trial.

Ellis described the case as "complex and unusual" and set the next hearing for January 15.

The veteran judge said he wanted the trial to be held "as soon as possible" but "time is required in order to achieve the ends of justice in this case."

Besides the deaths of the four Americans, Elsheikh and Kotey are also suspected of involvement in the killing of two Britons, Alan Henning and David Haines, and several other hostages including two Japanese nationals.

El Shafee Elsheikh (L) and Alexanda Kotey (R), members of the Islamic State kidnapping cell dubbed the "Beatles,"  pleaded not guilty in a US court
El Shafee Elsheikh (L) and Alexanda Kotey (R), members of the Islamic State kidnapping cell dubbed the "Beatles," pleaded not guilty in a US court Syrian Democratic Forces / Handout

Kotey and Elsheikh's four-member IS cell was dubbed the "Beatles" by their captives due to their British accents.

Britain stripped them of their UK nationality but their transfer to the United States was made possible only after the US authorities assured London they would not seek the death penalty.

Britain handed over evidence against the pair to the US authorities last month after receiving the assurance.

The two former British nationals had been in the custody of US forces in Iraq since October 2019 after being captured in January 2018 by Syrian Kurdish forces.

The eight-count US grand jury indictment charges them with various crimes including hostage-taking, conspiracy to commit murder and other offenses.

Assistant Attorney General John  Demers announces the transfer of two of the Islamic State members known as the "Beatles" to the US for trial
Assistant Attorney General John Demers announces the transfer of two of the Islamic State members known as the "Beatles" to the US for trial POOL / JIM WATSON

If convicted, they face a maximum sentence of life in prison.

According to the indictment, Kotey and Elsheikh were involved in abducting American, European and Japanese hostages in Syria from 2012 to 2015 along with two other British members of the "Beatles."

They allegedly tortured and killed their victims, including by beheading, and the IS released videos of the murders for propaganda purposes.

Alleged ringleader Mohamed Emwazi, known as "Jihadi John," was killed in a US airstrike in Syria in November 2015 while the fourth "Beatle," Aine Davis, is imprisoned in Turkey after being convicted on terrorism charges.

According to US authorities, the London-born Kotey and the Sudanese-born Elsheikh traveled to Syria from Britain in 2012 after being radicalized in Britain.

Kotey and Elsheikh supervised detention facilities for hostages and allegedly coordinated ransom negotiations conducted by email, according to the US authorities.

The pair also engaged in a "prolonged pattern of physical and psychological violence against hostages," they said.

"The cell was infamous, even inside ISIS, for their cruel and harsh methods," Anne Speckhard and Ardian Shajkovci of the International Center for the Study of Violent Extremism in Washington said in a report.

"There seemed to be no bounds to their sadistic methods, including crucifixion, waterboarding and tormenting their hostages with mock executions."

The families of Foley, Kassig, Sotloff and Mueller have welcomed the transfer of the two IS members to the United States to face justice.

"James, Peter, Kayla and Steven were kidnapped, tortured, beaten, starved, and murdered by members of the Islamic State in Syria," the families said in a joint statement. "Now our families can pursue accountability for these crimes against our children in a US court."

"We are hopeful that the US government will finally be able to send the important message that if you harm Americans, you will never escape justice," they said. "And when you are caught, you will face the full power of American law."

The families had lobbied to have the pair brought to the United States to be tried in a court of law rather than transferred to Guantanamo Bay in Cuba, where other prisoners in the US "war on terror" have been held.