The Islamic State (IS, formerly ISIS) released a video on Tuesday which shows the beheading of American journalist James Foley, who disappeared in November 2012 in Syria, CNN reports.
The video posted on YouTube contained a message to the United States to end its military operations in Iraq.
In the video, Foley is seen kneeling next to a man dressed in black. He reads a message, presumably scripted by his captors, that his "real killer'' is America.
"I wish I had more time. I wish I could have the hope for freedom to see my family once again," Foley can be heard saying in the video, according to CNN.
He is then shown being beheaded.
The National Security Council told CNN it is aware of the video.
"The intelligence community is working as quickly as possible to determine its authenticity. If genuine, we are appalled by the brutal murder of an innocent American journalist and we express our deepest condolences to his family and friends. We will provide more information when it is available," the agency said.
Foley disappeared in November 2012 in northwest Syria, near the border with Turkey. He was reportedly forced into a vehicle by gunmen; he was not heard from again. At the time of his disappearance, he was working for the GlobalPost.
According to the CNN report, the video also shows another American journalist. His life is said by the terrorists in the video to hang in the balance, depending on President Barack Obama does next.
The journalist is believed to be Steven Sotloff, who was kidnapped at the Syria-Turkey border in 2013. Sotloff is a contributor to Time and Foreign Policy magazines.
IS recently declared an Islamic caliphate in areas of Iraq and Syria that it captured. In Iraq, it has been conducting large-scale massacres and systematic rape, particularly against Yazidi minorities, drawing concerns of an impending genocide if rapid action is not taken.
Back when it was still known as the Islamic State of Iraq and the Levant, the group joined the fighting in Syria and made its presence known by torturing and murdering prisoners, among them children and teenagers, and forcing Druze men to convert to Islam or die.
In March, the group live-tweeted the amputation of a hand of a man charged with theft in the northern province of Aleppo.