Steven Sotloff. Twitter The group calling itself the Islamic State (also ISIS or ISIL) has released a video purporting to show the execution of American journalist Steven Sotloff, according to the SITE Intelligence Group.

Sotloff is the second American journalist brutally executed by ISIS in less than two weeks. On Aug. 20, the group released a video showing the execution of James Foley during which they also promised to execute Sotloff if the U.S. did not cease airstrikes against the group in Iraq.

The video of Sotloff, which was posted by SITE, was titled "A Second Message To America."

Footage was posted by SITE and seen by Business Insider. Shortly before the video was released, social-media accounts associated with Islamic State and its reporters also posted messages announcing a "second letter to America" would be published soon. Those messages included an encrypted link.

The video, set in a barren area, begins with footage of U.S. President Barack Obama speaking about the airstrikes that the U.S. launched against Islamic State last month. It goes on to show Sotloff in an orange jumpsuit and being held at knifepoint by a masked man while being forced to deliver a statement, a similar procedure that was used for Foley in the video of his execution.

In the clip, Sotloff recites remarks questioning America's current and past military operations in Iraq. Afterward, the masked man, who has a British accent, implies he was also the jihadist who was shown beheading Foley in the first clip.

"I'm back, Obama, and I'm back because of your arrogant foreign policy towards the Islamic State, because of your insistence in continuing your bombings," the man says in the video, adding, "Just as your missiles continue to strike our people, our knife will continue to strike the next of your people."

The footage ends with the masked jihadist standing next to another man in an orange jumpsuit. A caption identifies the man as "David Cawthorne Haines (British)."

"We take this opportunity to warn those governments who've entered this evil alliance of America against the Islamic State to back off and leave our people alone," the jihadist says.

Multiple media outlets in the U.K. have said British intelligence sources identified an English-Egyptian man named Abdel Majed Abdel Bary as one of three people suspected of being the jihadist from the Foley video. Bary, 23, is a former rapper who left to join jihadist fighters in Syria last year. His father is currently in U.S. federal prison charged with "conspiring with members of Al Qaeda ... in connection with the 1998 bombings of the U.S. Embassies in Kenya and Tanzania." American officials have declined to comment on whether Bary is suspected of appearing in the Foley video.

In this handout image made available by the photographer, American journalist Steven Sotloff (with black helmet) talks to Libyan rebels on the Al Dafniya front line, 25 km west of Misrata on June 2, 2011, in Misrata, Libya. Handout/Getty Images Just after Site reported the existence of the second video on Tuesday afternoon, White House press secretary Josh Earnest told reporters he was not immediately "in a position to determine the authenticity of the video." He said the White House's thoughts and prayers were with Sotloff's family.

"If the video is genuine, we are sickened," State Department spokeswoman Jen Psaki said. She said the intelligence community would work quickly to determine the video's authenticity.

James Foley. Nicole Tung Sotloff was kidnapped by militants upon crossing into Syria a little more than a year ago. He had been freelancing for Time and Foreign Policy magazines. Last week, his mother made an emotional plea to his captors and the Islamic State's self-proclaimed caliph, Abu Bakr al-Baghdadi.

U.S. officials have said that Sotloff and Foley were among fewer than 10 Westerners being held hostage by the group. When asked again on Tuesday, Psaki said "a few" U.S. citizens were being held by ISIS.

This post has been updated with new developments.