Video Of Steven Sotloff Slaying By ISIS Is Authentic, U.S. Confirms

The United States government said early Wednesday that the video showing the murder of journalist Steven Sotloff at the hands of an Islamic State militant is authentic.

According to the Twitter page run by President Barack Obama's National Security Council:

The video, which was discovered on Tuesday by the SITE Intelligence Group, showed Sotloff being beheaded in retaliation for U.S. airstrikes in Iraq. Prior to the slaying, Sotloff was shown kneeling on the ground and wearing orange clothing, a scene that was reminiscent of the Islamic State murder of American journalist James Foley two weeks ago.

The masked militant on the video warned President Barack Obama that as long as U.S. airstrikes against the militant group continue, "our knife will continue to strike the necks of your people." He also threatened the life of David Haines, a British citizen and aid worker, who was kidnapped in March 2013.

Sotloff, a 31-year-old freelancer for Time magazine and Foreign Policy, was abducted in 2013 while covering the civil war in Syria.

UN Secretary General Ban Ki-moon called Sotloff's murder a "despicable crime," the BBC News reported.

Secretary of State John Kerry issued a statement Wednesday, calling the killing of Sotloff "unfathomable" and "an act of medieval savagery by a coward hiding behind a mask."

"When terrorists anywhere around the world have murdered our citizens, the United States held them accountable, no matter how long it took," he said. "And those who have murdered James Foley and Steven Sotloff in Syria should know that the United States will hold them accountable too, no matter how long it takes."

Islamic militants are believed to be holding several more journalists in captivity, most of them Syrian reporters.