BANJA LUKA - Serbs in Bosnia headed to the polls on Sunday to decide whether to mark their “national holiday”, in a referendum that has placed the country’s fragile institutions under pressure.

The vote is the brainchild of Milorad Dodik, nationalist leader of the Bosnian Serb-run entity Republika Srpska (RS).

He has ignored a veto by Bosnia’s constitutional court, disapproval by the United States and the European Union and the reservations of Serbia, RS’ big ally.

Some 1.2 million voters are entitled to cast a ballot on whether they want their “national holiday” to continue to be celebrated on January 9. Polls opened at 7:00 am local time (0500 GMT) and are to close at 7:00 pm (1700 GMT).

“I came to vote because every nation and every state has its own national holiday. Accordingly, our Serbian people must have their holiday,” said Vojo Vujakovic, 60, at a polling station near the Bosnian Serb capitol of Banja Luka.

The date has huge emotional resonance in Bosnia, stirring memories of nationalist fervour, trauma and bloodshed.

It marks the proclamation of a “Republic of Serb people” in Bosnia that took place three months before the inter-ethnic 1992-1995 war that claimed 100,000 lives. The founders of that “republic” included Radovan Karadzic - sentenced in March to 40 years’ jail for genocide and crimes against humanity committed during the war that also displaced more than two million people.

Bosnia’s constitutional court has cancelled the referendum, ruling that the holiday is illegal for discriminating against non-Serbs, but Dodik pressed ahead defiantly.

“The Republic is going into a referendum. It’s a great day for our Republic and our people,” Dodik said on Friday after a trip to Moscow, where he met Russian President Vladimir Putin.

“We have to show our dignity, that we are a democratic people and that we have the right to make our own decisions,” he said.

The Dayton peace agreement that ended Bosnia’s war split the country into two semi-independent entities - the RS and a Muslim-Croat Federation.

But analysts say that the institutional bonds between the entities remain weak and prone to instability.

Some fear Dodik is warming up for a referendum on the independence of RS, which he has repeatedly threatened to carry out.

Bosnian Muslim leader Bakir Izetbegovic has accused Dodik of “playing with fire”, and a wartime commander of Bosnian Muslim forces, Sefer Halilovic, has accused him of “crossing the red line.”

But some commentators say a conflict is unlikely and a crisis is being stoked to boost nationalists’ chances in upcoming local elections.

Anecdotal evidence points to strong support from the public for the vote.

“We are all going to take part, to preserve our freedom, peace and dignity,” Vida Kojic, a pensioner in Lukavica, a suburb of Sarajevo that lies in the RS, told AFP.

Many roadsides in the RS had placards urging people to turn out and cast their ballot, and some signs portrayed Dodik along with the message, “The force of Srpkska.”