The referendum, on whether to mark January 9 as “Statehood Day” in the Serb Republic part of Bosnia, will be the first since a 1992 plebiscite on secession from then-Yugoslavia that ignited three years of ethnic war in which 100,000 were killed.
Polling stations across the Bosnian Serb-dominated region opened at 0700 a.m. (0500 GMT) and will close at 1900 (1700 GMT). Organizers said the first preliminary results were expected within 48 hours after the vote.
The Sarajevo-based Constitutional Court has ruled that the holiday would be illegal because it coincides with a Serbian Orthodox Christian holiday and so discriminates against Muslim Bosniaks and Catholic Croats living in the Serb Republic. The court also banned the referendum.
January 9 is the date when Bosnian Serbs declared independence from Bosnia in 1992, precipitating the country's devastating war marked by mass killings and persecution of Bosniaks and Croats in the territory they earmarked to become exclusively Serb.
The region's government has said it would comply with the court's ruling on the “Statehood Day” and make changes to its law on holidays to ensure it was not discriminating against other peoples - but only after the vote.
