Preliminary results early Monday morning show that nationalist parties, including one that wants to break away from Bosnia, easily won local elections held in Bosnia.

Voters were picking mayors and municipal councils in both of Bosnia's two semi-autonomous regions. Those areas — the Republika Srpska and the Bosniak-Croat Federation — each have their own governments, presidents and parliaments, but are linked by shared federal-level institutions.

Election officials said slightly more than half of the approximately 3.2 million eligible voters cast ballots Sunday, and in the Bosniak-Croat Federation, the respective nationalist parties almost completely defeated their non-nationalist rivals.

In Republika Srpska, the pro-Russian separatist party that has governed for more than a decade, defeated a pro-European Union coalition that is no less nationalist. The Alliance of Independent Social-Democrats, led by Republika Srpska President Milorad Dodik, won 30 percent more municipalities than in the last elections.

The party campaigned on a promise of Republika Srpska's secession from Bosnia — something many nationalist Serbs have been seeking since Yugoslavia collapsed during the 1990s.

Dodik's opponents — the Alliance for Changes — focused their campaign on bread-and-butter economic issues, while accusing him of corruption and of throwing the region into poverty.

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But he managed to shift Serb voters' attention away from the corruption accusations by holding, a week before the election, a referendum in Republika Srpska over a disputed holiday celebrated in that region. Bosnia's constitutional court had banned the holiday because it discriminates against non-Serbs.

The court also banned the referendum, saying its rulings are final, but Dodik conducted it anyway, portraying the bans as attacks against the region's autonomy. This mobilized the Serbs and voters overwhelmingly approved the holiday, although non-Serbs mostly boycotted the vote.

"Republika Srpska won twice in just seven days," Dodik declared after the preliminary results were announced. "The response of our people was just impressive," he said.

Analyst Adis Arapovic said Dodik's referendum move helped carry him to victory on Sunday.

However, because he defied the top court in carrying out the referendum, the state prosecutor issued him a summons for Monday. Risking arrest, Dodik said he won't go.

Western countries have threatened him with sanctions, but he enjoys the support of Russia.