Cairo: Egypt is engaged in “intensive efforts” to establish the whereabouts of a Croatian kidnapped by Daesh militants who threatened to execute him, the foreign ministry said on Friday.

The announcement comes amid growing concern for the fate of Tomislav Salopek, who was threatened with execution by the end of Friday if Egypt does not release Muslim women held in its prisons.

Fears mounted on Friday over the fate of the Croatian.

Croatian President Kolinda Grabar-Kitarovic said she would talk to her Egyptian counterpart Abdul Fattah Al Sissi by telephone as the 48-hour deadline set by the militants on Wednesday neared.

“Be sure that we are really doing our best to solve this,” she was quoted as saying by state-run HINA news agency.

Egypt’s foreign ministry said it was making “intensive efforts” to establish the whereabouts of Tomislav Salopek, a 31-year-old working for French geoscience company CGG kidnapped last month.

The abduction — unprecedented for Egypt — has rattled foreigners working for multinational companies and underscored the militants’ reach despite a massive military campaign against Daesh.

Although it has been battling a Daesh insurgency in the sparsely populated Sinai Peninsula, the North African country has been spared the hostage-taking of foreigners and horrific executions carried out by militants in Syria and Libya.

Salopek’s father called on the kidnappers to release the father of two, as Croatian Foreign Minister Vesna Pusic travelled to Cairo to follow the case.

“I am asking the people who hold my son to let him return to his family, because his motive to go to your homeland was exclusively to earn bread for his children. Nothing else,” Zlatko Salopek told AFP at the family’s home in the eastern Croatian town of Vrpolje.

After a meeting between Egyptian Foreign Minister Sameh Shoukry and Pusic, Cairo said: “We will not spare any effort to find the hostage and guarantee his security.”

Salopek had appeared in an Daesh video released on the internet on Wednesday, kneeling next to a masked militant holding a knife.

He read out from a piece of paper that his captors would execute him within 48 hours if Cairo failed to release female prisoners, a key demand of Islamist militants over the past two years.

Thousands of people, mostly Islamists, have been jailed since the army overthrew Islamist president Mohammad Mursi in 2013 and unleashed a deadly crackdown on his supporters.