Bosnia and Herzegovina's general election on Sunday appears to have returned nationalist parties to the top, according to preliminary results reported by DW and The Guardian. Final official results could take days.

Milorad Dodik, the Bosnian Serb leader, declared victory for his party, the Alliance of Independent Social Democrats, known as SNSD, The Guardian reported. Early counts gave SNSD about 39% in Republika Srpska, the country's Serb-run region.

Bosnia has an unusual three-member presidency, with one Bosniak, one Croat and one Serb member. In early counts, Bosniak incumbent Denis Bećirović had about 38%, Croat candidate Filipović about 47% and Serb candidate Željka Cvijanović about 55%.

Dodik is a polarizing figure. He has pushed for years to weaken Bosnia's central institutions and has talked of Republika Srpska breaking away. He was barred from office last year after a court convicted him of defying the international envoy who oversees the peace deal. He remains the most powerful politician in the Serb region.

Here is the background. The 1995 Dayton peace agreement ended a war that killed about 100,000 people. It split Bosnia into two regions, the Serb-run Republika Srpska and a Bosniak-Croat federation, joined by weak national institutions. Elections often produce gridlock, because each group votes largely for its own parties.

Bosnia is a candidate to join the European Union, but progress has been slow. Western officials worry that rising nationalism could stall reforms and stoke tensions in the Balkans.

Turnout and the final makeup of parliament are still being counted.

What we know: Nationalist parties lead in preliminary results, and Dodik claims victory.
What we don't: The final presidency and parliament results, and how coalitions will form.