A Croatian hostage reportedly slain in Egypt was kidnapped by an unidentified group that demanded a ransom from his employer before turning him over to the Islamic State group, Croatia's Foreign Minister said Thursday.

Speaking in the Croatian coastal town of Rijeka, Foreign Minister Vesna Pusic said the original captors requested money from the French geoscience company that employed 30-year-old Tomislav Salopek.

The company says it received a ransom demand eight days after Salopek was kidnapped on July 22, but it included no phone number and multiple emails to the address it came from went unreturned.

On Aug. 5, a video emerged showing Salopek as a hostage of the Islamic State branch in Egypt. At that point, his captors demanded not money but the release of unspecified Muslim women from Egyptian jails.

"The conclusion was that there is no specific request and that we were dealing with two different organizations," Pusic said, "one that kidnapped him and the other that identified itself as the Islamic State."

The IS radio station announced Thursday that its Egyptian affiliate had killed Salopek, the first word from the extremist group a day after a gruesome image of his beheading circulated online.

Christophe Barnini, the chief spokesman for Salopek's employer, CGG, said that "at no moment did we enter negotiations with the kidnappers about a ransom."

The emailed ransom demand was not signed. For three days CGG sent replies to the email, in accord with Egyptian and Croatian authorities, Barnini said. The emails asked for proof of life and included a telephone number for the kidnappers to contact CGG, but they were never answered.

Authorities still have not confirmed that Salopek was killed and are continuing the search for him and his captors. It would be the first slaying of a foreign captive in Egypt, with the release of a video of him alive and then a photo of the alleged beheading, since the emergence of an Islamic State affiliate there. The government has been struggling to project an image of stability and revive the economy following years of unrest.

Pusic said she has met with representatives of about 80 other Croatian citizens working in Egypt and the government is considering stronger security measures for them, including the protection of the Egyptian army.

Islamic State militants in the Middle East and North Africa have taken a number of civilians hostage in recent years. Many European hostages have been released, reportedly in exchange for ransom, while citizens of the United States and Britain, which refuse to pay ransoms, have been killed. IS has released a number of graphic videos showing the beheading of hostages.

IS radio station Al-Bayan said that "soldiers of the Caliphate" killed Salopek, "whose country is participating in the war against the Islamic State."

It said the killing came after a deadline passed for "the renegade Egyptian government" to meet his captors' demands to free jailed women.