Milan Jelic, president of Bosnia's Serb Republic, has died of a heart attack, the prime minister said. He was 51.
Jelic died Sunday evening, said Bosnian Serb Prime Minister Milorad Dodik.
"President Jelic is dead. This is a sad day for Republika Srpska," Dodik told reporters, using the republic's official name.
Bosnia is divided into two ministates: the Bosniak-Croat Federation and the Serb Republic. Jelic, a Social Democrat, was elected president of the Serb Republic last year.
Serbian President Boris Tadic sent his condolences, saying Jelic was "a good president and a true friend of Serbia."
The vice president of the other Bosnian ministate, Muslim Bosniak Mirsad Kebo, said Jelic was "a good man and politician, who died too early at a time when he could have contributed the most."
Jelic was a member of the Serb Democratic Party — founded by wartime Bosnian Serb President Radovan Karadzic who is now a top war crimes fugitive — until 1998, when he switched to Dodik's party. Before he was elected president last year, he served as minister for economy, energy and development in the Bosnian Serb government.
The constitution was not clear about who may succeed Jelic, political analyst Tanja Topic said in Banja Luka, suggesting it could be Dragan Cavic, the former Bosnian Serb president and a member of the Serb Democratic Party, as he had received the second-most votes, after Jelic, in the last presidential elections. It could also be one of Jelic's deputies — Bosnian Croat Davor Cordas or Muslim Bosniak Adil Osmanovic.