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Sotloff beheading: Obama warning to Islamic State

3 September 2014 Last updated at 13:51 BST

President Barack Obama has vowed the US will not be intimidated, after Islamic State militants released a video showing the beheading of American journalist Steven Sotloff.

Mr Obama warned: "Our reach is long and justice will be served."

Another US journalist, James Foley, was similarly murdered last month.

BBC security correspondent Frank Gardner reports.