President Barack Obama has that the United States will not be intimidated by Islamic State (IS) militants after the beheading of a second American journalist.

The White House has determined that a video showing the brutal killing of freelance journalist Steven Sotloff is authentic.

Islamic militants have posted a video online which claims to show the beheading of US journalist Steven Sotloff, who went missing in Syria last year.

An internet video has been released purporting to show the beheading of US reporter Steven Sotloff by the Islamic State group.