'Pure evil' as IS beheads US aid worker Kassig

US President Barack Obama condemned as "pure evil" the Islamic State's beheading of American aid worker Peter Kassig after the group released a video showing his body Sunday.

Kassig's parents said they were "heartbroken" by their loss after IS made public the recording in a warning to Washington as it prepares to send more troops to Iraq.

"We are heartbroken to learn that our son, Abdul-Rahman Peter Kassig, has lost his life as a result of his love for the Syrian people and his desire to ease their suffering," Ed and Paula Kassig said in a statement posted on Twitter.

Kassig, who took the name Abdul-Rahman after converting to Islam, was captured last year and was threatened in an October 3 video showing the beheading of British aid worker Alan Henning. He was 26 years old.

"Abdul-Rahman was taken from us in an act of pure evil by a terrorist group that the world rightly associates with inhumanity," Obama said in a statement released by the White House aboard Air Force One as he returned home from an Asia tour.