Bosnian Serb police say they have detained several people suspected of trying to recruit for Islamic State.
The police also confiscated weapons and propaganda materials during the raids.
They come after a gunman shouting “Allahu Akbar” (God is Great) attacked a police station, killing an officer before being shot dead last week.
Bosnia-Herzegovina is made up of two semi-autonomous regions – the Bosnian Serb Republic and the Bosniak-Croat Federation.
Each has its own president, government, parliament, police and other bodies.
Police said the operation was carried out in several towns on Wednesday.
They did not provide the exact number of suspects arrested.