The group says it will kill Croatian national Tomislav Salopek if Egyptian authorities do not release "Muslim women" from prisons in 48 hours.
A new video apparently shows an Islamic State group threatening to kill a Croatian hostage.
In the footage, which was released on Wednesday, the terror group says it will kill married father-of-two Tomislav Salopek if Egyptian authorities do not release "Muslim women" held in Egyptian prisons.
"These matters have to be achieved before 48 hours from now," Salopek says in English in the video.
It was not clear who exactly the militants want released. There are thousands of Islamists and supporters of the Muslim Brotherhood group in prisons in Egypt.
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The video, which has been verified by The Associated Press, shows Salopek wearing a yellow jumpsuit and kneeling in the desert before a masked man carrying a knife. An Islamic State flag flies nearby.
In the video, Salopek identifies himself and says that Islamic State fighters captured him on July 22. If no action is taken, he will be killed, he says.
The footage was shot in the style of previous Islamic State propaganda videos in which they threaten and behead hostages.
Last year, the group killed hostages by beheading them, including U.S. aid worker Peter Kassig and U.S. journalists James Foley and Steven Sotloff.
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Croatia's Foreign Ministry previously said one of its nationals had been kidnapped in Cairo while on the way to work.
The company, France's CGG Ardiseis, works in oil and gas. It has a branch office in Cairo's Maadi suburb. According to his Linkedin profile, Salopek has been working for the company for nine months.
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