IS behead journalist Steven Sotloff

An Islamic State video has appeared which purports to show the beheading of Steven Sotloff, a US journalist being held hostage by the militants.White House spokesman Josh Earnest said US officials were checking the reports.

 Mr Sotloff disappeared in Syria in 2013. He appeared at the end of a video last month showing fellow US journalist James Foley being killed.

After Mr Foley's death, Mr Sotloff's mother appealed to IS leader Abu Bakr al-Baghdadi to save her son's life.