CAIRO – Police searches and diplomatic efforts intensified over the fate of a Croatian hostage held in Egypt by Islamic State extremists, who threatened to kill him Friday if the government did not release imprisoned Islamist women.

The group’s Egyptian affiliate said Wednesday that it would kill 30-year-old Tomislav Salopek in 48 hours if the Egyptian government did not release jailed “Muslim women” – a reference to those detained in the government’s crackdown on supporters of the Muslim Brotherhood and other Islamists.

As extremist sympathizers noted the passage of the deadline on social media, Croatia’s foreign minister, Vesna Pusic, met with her Egyptian counterpart in Cairo to press efforts. Foreign Minister Sameh Shourki’s office pledged in statement that Egypt “will spare no effort” in the search for Salopek.

No other information was immediately available about the fate of the hostage, a married father of two. In previous kidnapping situations involving the Islamic State group, deadlines have passed and videos of killings have appeared later.

Salopek, a surveyor in the oil and gas industry working with France’s CGG Ardiseis, was abducted in Cairo last month. The extremists’ videotaped demand, entitled “A Message to the Egyptian Government,” was shot in the style of previous Islamic State propaganda videos in which they threaten and behead hostages. It was the first time such a video had featured a foreign hostage in Egypt.