SARAJEVO (Reuters) - Bosnian Serb nationalist leader Milorad Dodik and Sefik Dzaferovic, the candidate of the largest Muslim Bosniak party, have won the Serb and Bosniak seats in Bosnia’s triumverate presidency, the election commission said early Monday.

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Moderate Croat Zeljko Komsic, who already served two terms in the presidency, won the Croat seat with 49.5 percent of the vote, winning over nationalist Dragan Covic from the largest Croat party, HDZ.

Dodik secured 55 percent of the vote and Dzaferovic 38 percent, based on about 42 percent of counted ballots, election commission President Branko Petric said at a news conference.

The turnout was 53.3 percent of voters, Petric said.

The ballot was a test for Bosnia to determine if it will progress toward European Union membership and NATO integration or remain held back by ethnic rivalries.

More than two decades after a war in which 100,000 died, leading Serb, Croat and Muslim Bosniak parties campaigned on nationalist tickets, reviving wartime pledges while failing to offer any clear economic or political visions.

About 1.7 million voters took part in the presidential and parliamentary elections, choosing members of Bosnia’s tripartite inter-ethnic presidency, consisting of a Bosniak, a Croat and a Serb, and lawmakers for parliament’s lower house.

They also voted for leaders and assemblies of its two autonomous regions - the Serb Republic and the Bosniak-Croat Federation, and of the federation’s 10 cantons.

Dodik, a pro-Russian leader who has repeatedly advocated secession of the Serb Republic and integration with Serbia, earlier proclaimed victory in his party stronghold in the northern town of Banja Luka.

Analysts believe that he will work to weaken the presidency.

“My first priority will be the position of the Serb people and of the Republika Srspka,” Dodik said, referring to Bosnia’s autonomous region that he has presided over until now.

“I believe that Bosnia-Herzegovina also may progress if everyone is respected,” he added.

Covic said he garnered the majority of Croat votes and that Komsic won only due to Bosniak votes. The HDZ had argued for the creation of new ethnically based election units in which Croats would vote only for their ethnic candidate.

“Such election results may cause an unprecedented crisis in Bosnia-Herzegovina,” Covic said in the southern town of Mostar.

There is a realistic possibility that the formation of the Federation parliament’s upper house may be blocked after the Bosniak and Croat parties failed to agree on how to change the election law before the vote.

The election commission will announce preliminary results of the parliamentary vote later on Monday.