President Barack Obama has confirmed the death of US aid worker Abdul-Rahman Kassig, whose beheading was shown in a video posted by Islamic State.
Mr Obama called the act “pure evil” and offered his condolences to the family of Mr Kassig, 26, who was abducted in Syria last year.
The video, authenticated by the White House, shows a masked man standing over Mr Kassig’s severed head.
It also shows a mass beheading of 18 Syrian troops.
The president praised Mr Kassig as a humanitarian and said he was “taken from us in an act of pure evil by a terrorist group that the world rightly associates with inhumanity”.
“Today we offer our prayers and condolences to the parents and family of Abdul-Rahman Kassig, also known to us as Peter,” he added.
Mr Obama’s comments came as he flew back to the US from Australia where he was attending the G20 summit.