The mother of Steven Sotloff, the second American journalist executed by the Islamic State, filmed an emotional plea for his release last week.

Mr Sotloff, who disappeared last year while working in Syria, was last seen in August in the execution video of fellow journalist James Foley.

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Shirley Sotloff appealed to the leader of the Islamic State, asking for him to be merciful and spare her 31-year-old son’s life.

A video purporting to show the beheading of Mr Sotloff was released overnight, with his executioner blaming American President Barack Obama for his death.