Police in Britain arrested a 38-year-old man at Luton Airport on terrorism charges on Wednesday, the Metropolitan Police said in a statement.
The BBC reported that the man arrested was Aine Davis, who has been accused of being part of an Islamic State (ISIS) cell that murdered hostages. The group of four men, who were with ISIS in Syria, was nicknamed "The Beatles" by hostages because of their British accents.
The police statement did not identify the person arrested. It said a man was arrested "in relation to offenses under sections 15, 17 and 57 of the Terrorism Act, 2000 and was taken to a south London police station, where he currently remains in police custody."
The BBC reported that Davis, of London, flew into Luton airport after his release from prison in Turkey where he was serving a seven-and-a-half-year sentence for a conviction on terrorism charges.
The Islamic State cell garnered international attention after releasing videos of the murders in 2012 through 2015 of four US citizens - journalists James Foley and Steven Sotloff and aid workers Kayla Mueller and Peter Kassig. Other victims included two British aid workers and two Japanese journalists.