Egyptian IS franchise claims to have beheaded Croatian hostage

The Islamic State group claimed on Wednesday to have beheaded a Croatian hostage abducted in Egypt, posting a picture on IS group-affiliated Twitter accounts which the group said showed the victim's body.

The still image, shared by Islamic State group sympathisers, appeared to show the body of Tomislav Salopek, a married, 30-year-old father of two, wearing a beige jumpsuit looking like the one he had worn in a previous video.

A black flag used by the Islamic State group 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", after a deadline had passed for the Egyptian government to meet the group's demands.

However, Croatian Prime Minister Zoran Milanovic said that authorities in Croatia cannot confirm Salopek's killing with certainty:

"We can not 100 percent confirm it is true, but what we see looks horrific. A confirmation may not come for several days."

Milanovic, in an address to the nation on Croatian television, also urged people not to expose their children to the gruesome online image of Salopek's body, and not to distribute it further.

Officials "will not stop searching, digging as long as there is a drop of hope", he said.

He also appealed for calm, saying Croatians "have to continue living normally".

It comes after Wilayat Sinai, the local Islamic State affiliate, set a Friday deadline for Cairo to free "Muslim women" - a term referring to female Islamist prisoners detained in a sweeping government crackdown following the 2013 military ousting of Egypt's Islamist president. 

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 extremism" and another saying "Croatia reiterated its support for the Kurdistan region".  

Egyptian Foreign Ministry officials were not immediately available for comment. An official at the Croatian Embassy in Cairo who refused to give his name said the embassy could not comment on the incident. 

The Islamic State group holds about a third of Iraq and neighbouring Syria in its self-declared "caliphate". In Syria, IS militants have killed foreign journalists and aid workers, including US journalist James Foley in August last year.  

Foley's taped beheading was followed by the killing of US-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.