Steven Sotloff beheading shown in video, ISIS claims

The militant Islamic State in Iraq and Syria (ISIS) has released a video it says shows the beheading of U.S. journalist Steven Sotloff, according to the website Siteintelgroup.com.

A video of reporter James Foley's beheading released in August also showed Sotloff, warning he would be killed next if U.S. airstrikes continued.

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The reports cannot yet be confirmed, Pentagon press secretary Rear Admiral John Kirby told reporters Tuesday afternoon.

"The video is similar in how it looks," said CBC'sLyndsay Duncombe after viewing the video. "It's in a desert. The man who is beheaded is wearing an orange jumpsuit."

The ISIS militant in the video blames the beheading on U.S. President Barack Obama's decision to continue airstrikes in Iraq.

On Tuesday, U.S. Central Command said in a written statement that U.S. military forces conducted one airstrike near the Mosul Dam on Monday, destroying or damaging 16 ISIS armed vehicles.

The strike was conducted under authority to protect U.S. personnel and facilities, support humanitarian efforts, and support Iraqi forces that are acting in furtherance of these objectives.

U.S. Central Command has conducted a total of 124 airstrikes across Iraq.

The man believed to be Sotloffspeaks in the video, she said. CBC policy prohibits the network from broadcasting statements made under duress.

The next step is for officials to identify whether or not the man is Sotloff,Duncombe said.

White House officials said the process of verifying the man's identity has begun.

"If there is a video that has been released, it is something that will be analyzed very carefully by the U.S. government and our intelligence officials to determine its authenticity," Josh Earnest, a White House spokesman, said.Earnest added he was not in a position to confirm the video's authenticity at this point.

"The intelligence community is working as quickly as possible to determine its authenticity," Bernadette Meehan, the U.S. National Security Council spokeswoman, confirmed. More information will be provided when it is available, she said in a written statement.

Another man, described as British, is shown at the end of the video. He is identified as the next intended victim if the airstrikes continue.

Family is 'grieving privately'

Sotloff's family is aware of the video, a family spokesman said.

Barak Barfi released a two-sentence statement, saying Sotloff's family "knows of this horrific tragedy and is grieving privately," reported The Associated Press.

Before his capture near Aleppo, Syria, in August 2013, freelance reporterSotloff, 31, had contributed to Time magazine and other periodicals. He was born in Miamiand travelled extensively throughout the Middle East.

"We are shocked and deeply saddened by reports of Steven Sotloff's death,"Time editor Nancy Gibbs said in a statement, adding that "he gave his life so readers would have access to information from some of the most dangerous places in the world."

Gibbs expressed her condolences to his family.

Last week, Sotloff's mother, Shirley, made a recorded video plea to her son's captors, pleading for his release.

She asked his captors to be merciful and not punish her son for matters he has no control over.

'Pure barbarism,' CPJ says

The Committee to Protect Journalistsreleased a statement condemning the action.

War reporting is dangerous and journalists know that, the statement reads.

"But being butchered in front of camera simply for being a reporter is pure barbarism," saidCPJexecutive director Joel Simon in the statement. He saidSotloffand Foleywere civilians.

"Their murders are war crimes and those who committed them must be brought to justice swiftly," he said.

Prime Minister Stephen Harper also called the act barbaric. "Appalled to learn of the barbaric and unacceptable death of Steven Sotloff at the hands of [ISIS]," he tweeted, expressing his condolences to Sotloff's loved ones.

• On mobile? See Stephen Harper's tweet

British Prime Minister David Cameron called it a "despicable and barbaric murder" if verified. He tweeted that security officials were briefing him.

• On mobile? See David Cameron's tweet

Cameron will chair an emergency response meeting with his Cabinet early Wednesday, the Associated Press reported.

For the past two years, Syria has been the most dangerous country for reporters, according to CPJ.

At least 70 war reporters have died covering the conflict, and another 80 journalists have been kidnapped.