The ISIS-loyal group Sinai Province claimed Wednesday to have executed a Croatian hostage thought to be Tomislav Salopek. Pictured: A man purported to be an Islamic State captive is seen standing in a cage in this still image from an undated video earlier this year. Reuters

Extremists linked to the Islamic State group claimed Wednesday to have beheaded a Croatian hostage whom the militants threatened to execute if Muslim women in Egyptian jails weren't released. The Sinai Province, a militant organization with ties to the Islamic State, also known as ISIS, posted a photo online of a body thought to be 30-year-old Tomislav Salopek, Reuters reported.

Salopek, a father of two, was working in Cairo when he went missing last month. Officials had not yet confirmed the authenticity of the photo circulating Wednesday, Express reported.

A man identifying himself as Salopek appeared in a hostage video last week. He read from a script and demanded the freedom of all female Muslim prisoners. The photo Wednesday showed a body in a similar jumpsuit to the one Salopek was wearing, with a black ISIS flag nearby, the Washington Post reported.