Health authorities said they are trying to establish the source of infection as the two people had not traveled abroad. They most likely got the virus at a business gathering they both attended, officials said.
The infected people had a fever and ``felt as if they had been run over by a train,`` but did not have other more serious symptoms, epidemiologist Bernard Kaic said at a press conference.
Kaic said authorities expect more omicron cases to emerge in the coming days and weeks.
Croatia, along with much of Central and Eastern Europe, faced a major surge in infections this fall that has started to ease in recent days. The country confirmed 728 new infections in the past 24 hours while 51 more people have died.
Croatia has vaccinated about 54% of its population of 4.2 million, a much lower figure than the EU average.
More than 11,000 people with COVID-19 have died in Croatia.