A member of the notorious Islamic State kidnap-and-murder cell known as the "Beatles" was sentenced to life in prison by a US court on Friday for the deaths of four American hostages in Syria.

El Shafee Elsheikh, 34, was given eight concurrent life sentences after being convicted in April of hostage-taking, conspiracy to murder US citizens and supporting a terrorist organization.

District Court Judge T.S. Ellis said Elsheikh's conduct "can only be described as horrific, barbaric, brutal, callous and, of course, criminal" as he handed down the sentence in Alexandria, Virginia.

Elsheikh, wearing large glasses, a black face mask and a dark green prison jumpsuit, gave no visible reaction to the sentencing.

The two-week trial of the former British national, which featured emotional testimony from former hostages and parents of the victims, was the most significant prosecution of an IS militant in the United States.

Diane Foley, mother of murdered hostage James Foley, in a statement to the court on Friday addressed Elsheikh, saying "your hate-filled crimes did not win... You have been held accountable for your depravity.

"Love is much stronger than hatred. I pity you Elsheikh for choosing hatred."

At the trial, the jury had deliberated for less than six hours before finding Elsheikh guilty for his role in the deaths of four Americans -- journalists Foley and Steven Sotloff and aid workers Peter Kassig and Kayla Mueller.

Elsheikh and another former "Beatle," Alexanda Amon Kotey, were captured by a Kurdish militia in Syria in January 2018 and handed over to US forces in Iraq.

They were flown to the United States in 2020 to face trial.

Kotey, 38, pleaded guilty in September 2021 and was sentenced to life in prison in April.

Another alleged "Beatle," Aine Davis, 38, has been deported to Britain from Turkey and remanded in custody on terrorism charges.

The fourth "Beatle," executioner Mohammed Emwazi, was killed by a US drone in Syria in 2015.

The hostage-takers, who grew up and were radicalized in London, were nicknamed the "Beatles" by their captives because of their distinctive British accents.

Active in Syria from 2012 to 2015, they are accused of abducting more than two dozen journalists and relief workers from the United States and other countries.

Ten former European and Syrian hostages testified at Elsheikh's trial accusing the "Beatles" of months of brutal treatment including beatings, electric shocks, waterboarding and mock executions.

Foley, Sotloff and Kassig were beheaded by Emwazi, and videos of their deaths were released by IS for propaganda purposes.

Mueller was initially held by the "Beatles" but was later turned over to IS leader Abu Bakr al-Baghdadi, who reportedly raped her repeatedly.

IS announced Mueller's death in February 2015. The group said she was killed in a Jordanian airstrike, a claim disputed by US authorities.

Baghdadi died during a US special forces raid in 2019.

Ahead of Elsheikh's sentencing, British police revealed details on Wednesday of the years-long effort to identify the hostage-takers and bring them to justice.

Richard Smith, the head of London police's counter-terrorism unit, compared it to "putting together very small pieces of a jigsaw" and following a "trail of breadcrumbs."

Elsheikh declined to address the court on Friday but his attorneys said he intended to appeal the verdict on the grounds of "ineffective counsel."