Image appears to show man beheaded by 'IS' group

An online image purports to show a Croatian hostage held by Islamic State's Egyptian affiliate beheaded.

An online image has emerged which appears to show a Croatian hostage held by an Egyptian affiliate of the so-called 'Islamic State' group beheaded.

The still image, shared by 'IS' sympathisers on social media, showed the apparent 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 'IS' and a knife were planted in the sand next to him.

The photo carried a caption in Arabic that said Mr 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.

This comes after the 'IS' affiliate set a Friday 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 an 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.

'IS' 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, starting with American journalist James Foley in August last year.

Mr 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.