The fate of a Croatian abducted by the extremist Islamic State group near Cairo was unknown on Saturday, hours after a two-day deadline set by the jihadists to execute him apparently passed without any news of his current condition.
Egypt's foreign ministry said it was making "intensive efforts" to locate Tomislav Salopek, a 31-year-old working for French geoscience company CGG kidnapped last month.
Salopek appeared in an IS 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.
The video did not specify when the countdown began, but more than 48 hours have passed since it was put online, with no word early Saturday on whether the execution had been carried out.
The abduction -- unprecedented for Egypt -- has rattled foreigners working for multinational companies and underscored the jihadists' reach despite a massive military campaign against IS.
Although it has been battling an IS insurgency in the sparsely populated Sinai Peninsula, the North African country has been spared the hostage-taking of foreigners and horrific killings carried out by jihadists in Syria and Libya.
Salopek's father appealed to the kidnappers to release the father of two, as Croatian foreign minister Vesna Pusic travelled to Cairo for emergency talks.
"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 talks between Egyptian foreign minister Sameh Shoukry and Pusic, Cairo said: "We will not spare any effort to find the hostage and guarantee his security."
Thousands of people, mostly Islamists, have been jailed since the army overthrew former Islamist president Mohamed Morsi in 2013 and unleashed a deadly crackdown on his supporters.
Kidnapped from car
Salopek was abducted last month on a road running from the west of Cairo. His driver was left unharmed, and police say they have questioned him.
In his hometown, neighbours were braced waiting for news of Salopek, described as a friendly young man.
"I think that every inhabitant of Vrpolje is very upset and sad, fearing the outcome. We fear the worst, but we all have a hope that it will end well after all, although time is running out," neighbour Miro Hrastovic said.
It was not clear where the militants were holding him in the vast and mostly-desert country, which shares a long border with conflict-strewn and lawless Libya.
While the jihadists operate mostly in Sinai, northeast Egypt, they have also conducted attacks in the western desert over the past two years although these have abated after a series of police raids.
"Was this individual actually grabbed by people in (IS's Egypt affiliate) or was he grabbed by a criminal gang that sold him to people in Libya?" said Zack Gold, a visiting fellow with the Tel Aviv-based Institute for National Security Studies.
Formerly known as Ansar Beit al-Maqdis, the group changed its name to Sinai Province when it pledged allegiance to IS in November.
In December, it claimed responsibility for the murder of an American working for petroleum company Apache, also west of Cairo.
Last month, IS said it was behind a car bombing at the Italian consulate in Cairo -- the first such attack against a foreign mission in Egypt since jihadists began their campaign following the crackdown on Islamists.
Salopek's video was released the day before a lavish ceremony at the Suez Canal to celebrate an expansion of the waterway.
"The purpose of it, although it was called 'A message to the Egyptian government', was a message to foreign countries doing business" in Egypt, Gold said.
President Abdel Fattah al-Sisi, who as the army chief toppled Morsi, pledged at the ceremony to "defeat" the militants.
The army says it has killed more than 1,000 of them, but the insurgency in Sinai which neighbours the Gaza Strip and Israel appears unabated.
The jihadists have killed hundreds of soldiers and policemen, and they even destroyed a navy vessel with a wire-guided missile last month.