SARAJEVO, Bosnia and Herzegovina — A pro-Russia Serbian nationalist claimed victory in the race for the Serbian seat on Bosnia’s three-member presidency on Sunday but official results will not be announced until Monday morning.
A victory for Milorad Dodik, a Bosnian Serb strongman and a close ally of Russia’s president Vladimir V. Putin, could exacerbate ethnic rivalries in the Balkan nation and stall the country’s bid for membership in the European Union.
The president of the country’s election commission, Branko Petric, confirmed that with 44 percent of the vote counted, Mr. Dodik was leading in the race for the Serbian seat in the country’s tripartite presidency.
“It’s a clear cut victory,” Mr. Dodik said in Banja Luka, the capital of the Serbian autonomous region of Bosnia. “I don’t care who the other two representatives in the presidency are. I am going there, to this presidency, to work above all and only for the interests of Serbs.”
Mr. Dodik has campaigned for years for the Serbian region he has ruled for nearly two decades to break away from Bosnia. He is running against the incumbent, Mladen Ivanic, a moderate who wants the Serbian region to remain part of Bosnia.
In an electoral system designed as part of the Dayton Accords that ended the Bosnian war in 1995, the presidency is shared by a Croat, a Serb and a Muslim. A member of each ethnic group is assured of winning a presidential seat, with the chairmanship rotating every eight months.
In the race for the Croat seat, Dragan Covic, the hard-line incumbent who shares Mr. Dodik’s goal of further fragmenting Bosnia into ethnic enclaves, conceded defeat. Mr. Covic, who was backed by the Croatian government in Zagreb and increasingly Mr. Putin, had been seeking to establish a Croat-only entity in Bosnia.
He lost to a moderate rival, Zeljko Komsic. Mr. Komsic struck a conciliatory note in his address, saying that he would work for Bosnians of all ethnic groups.
“Bosnia is my country and it’s my duty, my ethical obligation, to work in this position for all citizens with the two members of the presidency,” he said.
The leader for the Muslim seat was Sefik Dzaferovic, a member of the Muslim constituency’s biggest party, the Party of Democratic Action, and a loyal follower of its leader, Bakir Izetbegovic, who has served two terms and could not run for a third.
The Dayton Accords left the country divided between a Serbian autonomous region and a Croat-Muslim federation. In addition to the presidency, there are also three Parliaments, 11 prime ministers and as many local governments.
The complicated system has given Moscow ample opportunity to exploit divisions as it tries to amplify its influence on Europe’s periphery. Mr. Putin has backed politicians who would destabilize Bosnia’s fracturable institutions, still largely run by the European Union.
“Bosnia is a very fragile, unconsolidated democracy with weak institutions that can easily be undermined,” said Adnan Huskic, an independent political analyst in Sarajevo.
The European Union has imposed sanctions on the Kremlin over Russia’s annexation of Crimea. Interfering in Bosnia may be Mr. Putin’s payback.
Mr. Dodik, a close ally of Mr. Putin’s, had been president of the Serb ministate, an autonomous region that he had declared independent. Because of term limits in the Serbian region, where he had already served two terms as president and two as prime minister, he turned his attention to the Bosnian presidency.