The Islamic State group claims to have beheaded a Croatian hostage abducted in Egypt, posting a purported picture of the victim's body on IS-affiliated Twitter accounts.
The Croat, Tomislav Salopek, was abducted last month west of the capital Cairo. The jihadists had issued a 48-hour deadline that ended last Friday (local time) threatening to kill him if Muslim women prisoners were not released from Egyptian jails.
The picture's authenticity could not be immediately verified.
His abduction and purported killing were unprecedented in Egypt, which is battling an IS insurgency in the eastern Sinai Peninsula.
State-run Croatian news agency HINA on Wednesday quoted a foreign ministry source as saying it "does not have confirmation that abducted Croatian citizen Tomislav Salopek has been killed."
The picture was posted on IS-affiliated Twitter accounts with the caption: "Execution of prisoner from Croatia – which has participated in war on Islamic State – after deadline ended."
Salopek, a 31-year-old father of two, had been working with French geoscience company CGG when abducted from a car roughly 22km west of Cairo, security sources told AFP.
Egypt had said it was intensifying efforts to locate Salopek after IS released a video of the hostage last Wednesday.
In the video, Salopek, kneeling next to a masked militant holding a knife, was forced to read a statement saying his captors would execute him in 48 hours if Cairo failed to release female prisoners, a key demand of Islamist militants over the past two years.
Salopek's abduction had been treated by police as a criminal kidnapping before the video emerged.
Although IS's Egyptian affiliate has killed hundreds of policemen and soldiers, the country had been spared the gruesome kidnappings and executions of foreigners conducted by IS in Iraq and Syria.
Salopek's father had appealed to the kidnappers to release him and Croatian Foreign Minister Vesna Pusic had travelled to Cairo for emergency talks.