Sarajevo, Bosnia-Herzegovina: Bosnia’s state prosecutor has opened an investigation into a Bosnian Serb referendum that was held in violation of the constitution, he said Monday.

A statement from Chief Prosecutor Goran Salihovic said the case will be treated as a “priority”, and certain people will be called for questioning.

Bosnian Serbs voted overwhelmingly Sunday in favour of keeping a disputed holiday that a constitutional court had said discriminates against non-Serbs. The court had also banned the referendum, which was organised by the local government in the Serb region of Republika Srpska.

Referendum organisers said that preliminary results showed 99.81 per cent of voters in Republika Srpska were in favour of the holiday and that turnout was 55.7 per cent. Non-Serbs living in Republika Srpska mostly boycotted the vote.

During the 1992-95 war — which killed 100,000 people and turned half of the country’s population into refugees — Bosniaks and Croats were persecuted and almost completely expelled from Republika Srpska’s territory.

The region didn’t gain independence after the war, but ended up as an autonomous part of Bosnia.

Bosniaks and Croats who returned there view the holiday as a celebration of their expulsion while Republika Srpska marks the day with religious ceremonies, hinting the region is still meant just for Serbs.

The West had called for the referendum not to be held, but the Bosnian Serbs were backed by Russia. Western officials said they might consider halting projects in the mini-state or impose travel bans on its leaders and freeze their assets.

Although facing charges as the initiator of the vote, Bosnian Serb leader Milorad Dodik celebrated the result with thousands of people, fireworks and Serb flags late Sunday in Pale, the wartime capital of Republika Srpska.

“I’m so proud … of all those who voted today, and I have to say — shame on all Serbs who did not show up at the referendum today,” he said at the gathering, hinting he expected a higher turnout.

Opposition parties in Republika Srpska claim Dodik scheduled the vote a week before a local election to divert campaign topics from corruption and poverty to nationalism.

“Obviously this was a pre-election gathering,” that costed tax payers 750,000 euros (Dh 3,084,858) and only served the interests of Dodik’s party, Bosnia’s foreign minister said of the referendum.

Bosnian Serb authorities said they plan to change their law on holidays in line with the constitutional court’s ruling, most likely so that the holiday stays but those who don’t want to celebrate don’t have to.

Even if this solves the dispute over the holiday, the referendum itself defies the constitutional court’s ban and violations of the constitution can be punished with a jail term of between six months and five years.