Islamic State (ISIS) has threatened to kill a Croatian father of two if Egypt does not release 'Muslim women' prisoners within the next 48 hours, in a new video published Wednesday.

The video, released on a jihadist website, shows 30-year-old Tomislav Salopek kneeling in an orange jumpsuit - in the style of previous 'pre-beheading' ISIS videos.

Salopek, reading from a script, stated that ISIS captured him on July 22. He mentioned that he works for a French company based in Cairo.

"They want to substitute me with the Muslim womens arrested in Egyptian prisons," he stated. "This matter have to be achieved before 48 hours from now, if not the soldiers of Wilyat Sina will kill me."

Wilyat Sina is ISIS's term for its branch in the Sinai desert. Formerly Ansar Bayt Al-Maqdis, the Islamist terror group declared allegiance to ISIS earlier this year.

The Sinai desert has become a battleground between terrorists and the Egyptian army, as the latter attempts to weed out Islamism within its borders after the downfall of the Muslim Brotherhood in 2013. Since then, dozens of Brotherhood supporters have been imprisoned.