WASHINGTON, Aug. 20 -- The entire world is appalled by the brutal murder of James Foley, U.S. President Barack Obama said on Wednesday, shortly after the authenticity of a video showing the American journalist's beheading had been verified.

Obama said he had spoken to the Foley family and told them that "we are all heartbroken at their loss, and join them in honoring Jim and all that he did."

Foley, a freelance American journalist who was captured by militants in Syria in November 2012, was shown on a video being beheaded by a masked militant from the Islamic State of Iraq and the Levant (ISIL) to avenge ongoing air raids on the group's targets by U.S. warplanes.

Obama praised Foley for being "a man who lived his work, who courageously told the stories of his fellow human beings and who was liked and loved by friends and family."

"Today, the American people will all say a prayer for those who loved Jim. All of us feel the ache of his absence. All of us mourn his loss," Obama said from Martha's Vineyard, Massachusetts during his vacation, shortly after the White House said that the video showing the beheading of Foley had been authenticated by the U.S. intelligence community.

ISIL militants, which have seized large swathes of territories in western and northern Iraq in recent months, also threatened to kill another man shown on the video said to be American freelancer Steven Sotloff.

The United States will continue to "do what we must do to protect our people," Obama said, vowing that "when people harm Americans, anywhere, we do what's necessary to see that justice is done."

The president also urged Iraqi people to continue their efforts to expel the terrorists from their communities and called on a common effort from governments and peoples across the Middle East to reject nihilistic ideologies.

"ISIL has no ideology of any value to human beings. Their ideology is bankrupt," he added.