A video posted online claims to show the beheading of United States aid worker Peter Kassig by the "Islamic State", Anadolu Agency reported.
The 26-year-old - who was captured in Syria in 2013 - had previously appeared at the end of a video showing the death of British hostage Alan Henning. Kassig - whose family have said has converted to Islam - is one of several men seemingly beheaded in the 15-minute long video.
It is still to be confirmed as genuine.