Images posted online seem to show a beheaded Tomislav Salopek, a Croatian national, officials from various countries and the SITE Intelligence Group said Wednesday.
As has been the case before with ISIS beheadings, there was no immediate or definitive proof such as DNA evidence that Salopek had been killed. CNN could not independently confirm the authenticity of the image.
Still, the image and a video released days ago threatening just a horrific act had many fearing the worst.
"We cannot confirm with 100% certainty that it is true," Croatian Prime Minister Zoran Milanovic said. "... However, what we have seen ... doesn't look good. It looks horrible."
