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.


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


In Washington, the White House said it couldn't confirm the authenticity of the video, Reuters reported.


Before his capture near Aleppo, Syria, in August 2013, freelance reporter Sotloff, 31, had contributed to Time magazine and other periodicals. He was born in Miami.


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



With files from Reuters