Japanese government working to authenticate video claiming ISIS execution

The Japanese government is working to authenticate a video posted online Saturday, purporting to be from the Islamic State group, which claimed one Japanese hostage had been killed, and demanded a prisoner exchange for the other.
The video was posted online Saturday, but was quickly deleted. Various differences in how it was released, compared to previous ISIS hostage videos, led to heightened scrutiny and skepticism.

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Militants on a website affiliated with ISIS disagreed about the message's authenticity. One militant warned that Saturday's new message was fake, while another said the message was intended only to go to the Japanese journalist's family. A third militant on the website noted that the video was not issued by al-Furqan, which is one of the media arms of ISIS, and has issued past videos involving hostages and beheadings. Saturday's message did not bear al-Furqan's log