A video purportedly released by Islamic State (IS) threatens to kill a Croatian hostage if Egyptian authorities do not release "Muslim women" held in prison within 48 hours.

The video, circulated on social media by IS sympathisers, shows a man wearing a yellow jumpsuit kneeling before a knife-wielding masked man in military fatigues.

Reading from a note, the man identifies himself as 30-year-old Tomislav Salopek, and says that IS fighters captured him on July 22.

If Egyptian authorities do not act, he says, he will be killed.

Croatia's Foreign Ministry said late last month that one of its nationals with the same initials had been kidnapped in Cairo.

It comes as Egypt prepares to unveil a new extension of the Suez Canal, an event it has been promoting for months.

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