Obama confirms Peter Kassig's death

The group on Sunday released a video showing the beheading of the aid worker Peter Kassig.

Kassig was a former Army Ranger who had disappeared from northeastern Syria more than a year ago.

In his statement, Obama said: "Today we offer our prayers and condolences to the parents and family of Abdul-Rahman Kassig, also known to us as Peter.  We cannot begin to imagine their anguish at this painful time."

"Abdul-Rahman was taken from us in an act of pure evil by a terrorist group that the world rightly associates with inhumanity.  Like Jim Foley and Steven Sotloff before him, his life and deeds stand in stark contrast to everything that ISIL represents.  While ISIL revels in the slaughter of innocents, including Muslims, and is bent only on sowing death and destruction, Abdul-Rahman was a humanitarian who worked to save the lives of Syrians injured and dispossessed by the Syrian conflict," he said.

"While ISIL exploits the tragedy in Syria to advance their own selfish aims, Abdul-Rahman was so moved by the anguish and suffering of Syrian civilians that he traveled to Lebanon to work in a hospital treating refugees.  Later, he established an aid group, SERA, to provide assistance to Syrian refugees and displaced persons in Lebanon and Syria.  These were the selfless acts of an individual who cared deeply about the plight of the Syrian people," the President said.

Condemning the incident, Obama said the militant's group's action represent 'no faith'.

"ISIL's actions represent no faith, least of all the Muslim faith which Abdul-Rahman adopted as his own.  Today we grieve together, yet we also recall that the indomitable spirit of goodness and perseverance that burned so brightly in Abdul-Rahman Kassig, and which binds humanity together, ultimately is the light that will prevail over the darkness of ISIL," he said.