Croatia says it fears the worst for one of its nationals, Tomislav Salopek, abducted in Egypt but cannot confirm he has been beheaded by militants affiliated to Islamic State.
PM Zoran Milanovic addressed the nation after an Egyptian jihadist group claimed it had killed Tomislav Salopek, who was seized three weeks ago.
A photo purporting to show his body was posted on Twitter by a user associated with the group called Sinai Province.
It earlier threatened to kill him unless Egypt freed jailed Muslim women.
The photo circulated online on Wednesday shows a decapitated body in what appears to be desert, beside a knife driven into the sand and the black banner used by IS.
The Croatian Prime Minister Zoran Milanovic held a press conference after reports that a graphic photograph was posted on Twitter
The caption says the Croatian, a father of two aged about 30, was killed “for his country’s participation in the war against Islamic State”.
He had been working as a surveyor for French geoscience company CGG, which is involved in the oil and gas industry.
Mr Salopek was seized while travelling about 22km (14 miles) west of Cairo on 22 July, security sources said.
If the death is confirmed, it would be the first time that jihadist militants in Egypt have beheaded a Western hostage since stepping up their campaign against the state two years ago.
Extensive military operations have been conducted in North Sinai after deadly attacks by militants
The Croatian government could not confirm Mr Salopek’s death “with 100% certainty”, Prime Minister Milanovic said.
“I am not sure if we will be in any position to confirm the news in the next few days, but what we can see doesn’t look good, it looks very bleak… I am afraid that the worst has happened.”
How can IS death claims be checked?
Mr Milanovic urged people not to share the gruesome image posted online.
He also stressed that Croatia would not take part in combat operations against IS.
Croatia has previously said that while it was part of the international coalition against IS in the political sense – as a member of the EU and Nato – it had no plans to send troops to fight IS.