In a video allegedly released today by the Islamic State group (ISIS), the organisation urged the Egyptian government release “Muslim women” held in prison, threatening with killing a Croatian hostage if their demands are not met within 48 hours.

The video, entitled titled “A Message to the Egyptian Government,” was released one day before the country plans to unveil a highly promoted new extension of the Suez Canal, and shows a Croatian hostage kneeling in the desert before a knife-wielding masked man in military uniform.

The hostage, who identifies himself as Tomislav Salopek, says the men who kidnapped him are part of Wilayat Sinai, a militant group based in the Sinai Peninsula that has pledged allegiance to ISIS, as the organisation’s black flag stands at full mast behind him.

“Soldiers of the Islamic State in the Caliphate of Wilayat Sinai caught me on Wednesday July 22nd,” Salopek says, reading off a small white paper."They want to substitute me with the Muslim women arrested in Egyptian prisons. These matters have to be achieved before 48 hours from now," he adds later. If the demands aren't met, the hostage says the militants will kill him.

Two weeks ago, Reuters had reported a Croatian man, identified as T.S. had been kidnapped in Cairo by armed men on Wednesday 22nd.

Salopek was working as a surveyor for the French company CGG in Cairo. According to Croatian officials, Salopek was going to work when a group of armed men stopped him, forced him out of his car, and drove away with him.

The minute-long video released by ISIS was uploaded to the anonymous file-sharing website, Archive.org, which militants have used in the past.