Returnee Ivo Bartulovic was killed in his home in the village of Barlovci a month ago.
The murder suspects are Croatian nationals, Croats from Plaski, and one of them also has Bosnian citizenship, the police said.
The head of the Croatian Interior Ministry's criminal police department, Darko Dundovic, said the police believed that the motive for the murder was gain because the victim was robbed.
Dundovic said that cooperation with the Bosnian Serb police had been successful also in two previous murder cases, one of which occurred in Banja Luka and the other in Nebljusi, Croatia.
Investigating judge Jasminka Jerinic-Musnjak said she expected to question the suspects today.