The Islamic State (IS) released a video, showing the execution of British aid worker David Haines.
The 44-year-old from Perth, was captured by militants in Syria last year. IS executed two American journalists in the last few weeks, saying it was in response to American air strikes on the group in Iraq. The militants had threatened to execute Haines in earlier videos, calling on the US and Britain to cease supporting the Iraqi and Kurdish armies.
Prime Minister David Cameron said the murder of an innocent aid worker was "despicable and appalling".
"It is an act of pure evil. My heart goes out to the family of David Haines who have shown extraordinary courage and fortitude throughout this ordeal.
"We will do everything in our power to hunt down these murderers and ensure they face justice, however long it takes," he added.
Read more here.
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