CAIRO – Islamic State sympathizers circulated an image Wednesday that appears to show the grisly aftermath of the beheading of a Croatian hostage abducted in Egypt, which if confirmed would mark the first such killing of a foreign captive in the country since the extremist group established a branch here last year.

The killing of the 30-year-old oil and gas sector surveyor likely will rattle companies with expatriate workers in Egypt and cast a cloud over President Abdel-Fattah el-Sissi’s attempts to boost international investment and tourism following years of unrest.

The still image, shared by Islamic State sympathizers on social media, appeared to show the body of Tomislav Salopek, a married, father of two, wearing a beige jumpsuit resembling the one he had worn in a previous video. A black Islamic State flag and a knife were planted in the sand next to him.

The photo carried a caption in Arabic that said Salopek was killed “for his country’s participation in the war against the Islamic State,” and after a deadline had passed for the Egyptian government to meet their demands.

The picture also contained an inset of two Egyptian newspaper reports, with one headline declaring Croatia’s support of Egypt in its war against terrorism and another saying Croatia reiterated its support for the Kurds, who have been battling the IS group in Syria and Iraq. Croatian troops fought in the U.S.-led coalition in Iraq and still serve in the NATO-led force in Afghanistan.

Egyptian Foreign Ministry officials were not immediately available for comment. Croatia’s Foreign Ministry said it could not confirm Salopek’s death, but the country’s prime minister, Zoran Milanovic, will be addressing the nation in couple of hours. And President Kolinda Grabar-Kitarovic said in a statement that she is cancelling all her pre-arranged activities for the day.

The Associated Press could not independently verify the image. However, it bore markings consistent with the filmed hostage demand that the group released last week.

In that video, the Islamic State affiliate set an Aug. 7 deadline for Egyptian authorities to free “Muslim women,” a term referring to female Islamist prisoners detained in a sweeping government crackdown following the 2013 military ouster of the country’s Islamist president.

The extremists’ videotaped demand was entitled “A Message to the Egyptian Government,” and was shot in the style of previous Islamic State propaganda videos. It came just a day before el-Sissi hosted a much-hyped ceremony with foreign dignitaries to mark the opening of a new section of the Suez Canal.

Salopek, a surveyor working with France’s CGG Ardiseis, was abducted on a highway west of Cairo last month. The company has an office in the leafy Maadi suburb, where many expats and diplomats live.

Last week, Croatian Foreign Minister Vesna Pusic met with her Egyptian counterpart in Cairo to press for Salopek’s release, while Egyptian Foreign Minister Sameh Shoukry’s office pledged in statement that Egypt would ” spare no effort” in the search for him.

The Islamic State group holds about a third of Iraq and neighboring Syria in its self-declared “caliphate.” In Syria, Islamic State militants have killed foreign journalists and aid workers, starting with American journalist James Foley in August last year, and released grisly videos of the beheadings.

Foley’s taped beheading was followed by the killing of American-Israeli journalist Steven Sotloff, British aid workers David Haines and Alan Henning, American aid worker Peter Kassig, as well as Japanese nationals Haruna Yukawa and Kenji Goto.

In Libya, an IS affiliate released a video in February showing its fighters beheading a group of Coptic Christians from Egypt. In April, another video showed them beheading and shooting dead groups of Ethiopian Christians.

Egypt has seen an increase in violence since the ouster of Islamist President Mohammed Morsi, with attacks by suspected Islamic extremists in both the Sinai Peninsula and the mainland focusing primarily on security forces.

Militants have also targeted foreign interests, including the Italian Consulate, which was hit with a car bomb last month. That came just days after another bomb killed Prosecutor General Hisham Barakat in an upscale Cairo neighborhood.

But this would be the first time the local Islamic State affiliate, referring to itself as the Sinai Province, has captured and then killed a foreigner in Egypt, a major escalation as the country tries to rebuild its crucial tourism industry after years of unrest following the 2011 revolt against autocrat Hosni Mubarak.

Last December, the affiliate claimed responsibility for the killing of an American oil worker with Texas-based energy company Apache Corp. Apache had said that previous August that one of its supervisors had been killed in an apparent carjacking in the Western Desert, part of Egypt’s mainland.

Associated Press writers Sarah El Deeb in Cairo and Darko Bandic in Pula, Croatia, contributed to this report.