Twin elections have left Serbians facing a run-off presidential poll on May 20 between incumbent pro-EU moderate Boris Tadic and nationalist Tomislav Nikolic but it's unclear which coalition will emerge in parliament.
Serbian voters angry about high joblessness slashed the ruling Democrats to 23 percent support in parliament, leaving right-wing Progressives slightly out front and Socialists as kingmakers.
Tadic's Democratic Party dropped sharply from the previous 38 percent it scored in the last elections of 2008.
The Socialist Party of the late strongman Slobodan Milosevic and now led by former interior minister Ivica Dacic doubled its vote to 16 percent in Sunday's parallel parliamentary poll.
Dacic und Tadic in 2008
Dacic, addressing supporters on Sunday night in Belgrade, laid his claim to becoming premier after his role in Tadic's previous Democrat-led pro-EU reformist coalition.
"Maybe Serbia doesn't know today who will be president, but it knows who will be prime minister," said Dacic.
A narrow victory was claimed by Nikolic's opposition Serbian Progressive Party, which got 24.7 percent. But analysts say Tadic's Democrats may have a greater chance of forming a multi-party coalition to continue governing.
Zoran Stojilkovic, an analyst, said Dacic' Socialists had "huge blackmailing potential."
"They are closer to the Democrats and they will have huge demands," he said. "The likeliest outcome is that the pro-European coalition will continue."
As he cast his vote on Sunday, Tadic, a 54-year-old former psychology professor, promised "better living standards for ordinary people."
"I expect that Serbia will continue on its reform path," said Tadic whose party's popularity has slumped amid economic downturn and alleged corruption among the ruling elite.
Tadic became Serbia's first non-communist leader since World War II in 2004.
Nikolic, who once said he would rather see Serbia become a Russian province rather than an EU member, has shifted his rhetoric in recent years from being anti-Western to pro-EU. He ran the opposition's election campaign on promises to generate jobs and attract foreign investments.
Tensions over Kosovo
On Sunday Nikolic said that Belgrade would not pursue membership of the EU if the bloc demanded that Serbia give up its claim on Kosovo.
Serbia still refuses to recognize the former province of Kosovo, which declared independence in 2008.
Tensions were high in northern Kosovo on Sunday as minority Serbs defied ethnic Albanian authorities to vote in the Serbian elections.
Milosevic died in his prison cell during his war crimes trial at a UN tribunal in the Netherlands in 2006.
ipj/mz (Reuters, AP, dpa)