Obama vows 'relentless' response to Foley killing

Barack Obama says the country will do anything necessary to see that justice is done.

FILE: A picture taken on November 5, 2012 in Aleppo shows US freelance reporter James Foley. Picture: AFP.

JOHANNESBURG - The family of beheaded American journalist James Foley have asked the public not to share the gruesome video of his death on social network sites.

The video of the journalist kneeling reading a message from his killers the Islamic State militants (ISIS) before being executed, has gone viral.

US President Barack Obama said at a special briefing on the matter last night the country will be "relentless" and will do anything that is "necessary to see that justice is done".

"We will continue to confront this hateful terrorism and replace it with a sense of hope and civility. That's what Jim Foley stood for. A man who lived his work and courageously told the story of his fellow human being and was liked and loved by his friends and family."

The US government says its military attempted an unsuccessful rescue operation to free American hostages being held captive in Syria by ISIS.

The mission was intended to free Foley and others held at an undisclosed location.

Meanwhile, Foley's family was apparently contacted a week ago by his captors.

Philip Balboni the CEO of the Global Post, one of the publications for which Foley worked, says an e-mail was sent to his family, warning he was to be killed.

"On Wednesday night of last week, the Foley family received an email from the kidnappers that was full of rage against the United States for the bombing and they stated they would execute Jim."

Foley was abducted in 2012 by ISIS militants while he was working in Syria.