Serbs have voted in the country's first general election since its union with Montenegro was dissolved last year.
The nationalist Serbian Radical Party (SRS) has a clear lead in the country's elections, early projections suggest.
The basic choice for the 6.5m eligible voters was between the hardline nationalists and parties that are more pro-European and pro-reform.
The Centre for Free Elections and Democracy, a monitoring body, said the radicals had taken 28.5% of the vote.
As he voted, PM Vojislav Kostunica said the best way for a better life was for Serbia to continue on its current path.
The SRS candidate for prime minister, Tomislav Nikolic, urged the government to resign - but it is unclear whether he can form a governing coalition.
One difficult issue remains Kosovo, with the UN expected to rule on the future of the province this year.
The pro-reform Democratic Party (DS) and Democratic Party of Serbia (DSS) were credited with 22% and 17%.
Polling stations closed at 2000 (1900 GMT), with initial results expected late on Sunday evening.
After the first projections were announced, Mr Nikolic said: "We have won as we had expected."
More than 30% of voters had turned out in the first seven hours, Serbia's Election Commission said.
"Despite running against the parties led by the prime minister and the president (Boris Tadic) and their vicious campaigns against us, we proved our strength," Mr Nikolic said.
Coalition expected
He ruled out a coalition with the governing DS and DSS but on the subject of coalitions with other parties he said: "Let's wait and see the final results. Things are clearer after a night's sleep. We will see what will happen."
The BBC's Nick Hawton in Belgrade says the campaign has been largely devoid of the issues that have dominated in the past, such as co-operation with The Hague war crimes tribunal and Kosovo.
The SRS ruled the country under late leader Slobodan Milosevic during the 1990s.
The main choice is between nationalists and pro-reform partiesInstead other concerns such as the economy, privatisation, European integration and corruption have taken centre stage.
Prime Minister Vojislav Kostunica, who heads the conservative DSS, had urged citizens to vote - it was, he said, the best way to keep the country on a safe and stable path.
Voting was expected to be split between President Boris Tadic's pro-European Democratic Party (DS), Mr Kostunica's Democratic Party of Serbia (DSS) and war crimes suspect Vojislav Seselj's nationalist SRS.
President, Boris Tadic, whose Democratic Party is challenging the prime minister, said he hoped the outcome would produce a government capable of major reforms
Opinion polls have indicated that no party will win a majority outright but the president and prime minister are expected to form a coalition.
The poll was overshadowed by the issued of Kosovo, with the UN expected to rule on the future of the province this year.
The higher turnout has been caused by civic organisations putting a lot of effort into raising awareness of how important the elections are Pollster Marko Blagojevic The disputed province of Kosovo will be the first priority for any incoming government, our correspondent says.
The UN's chief envoy for the province is due to give his recommendations for its future soon after the election.
Branko Ruzic, chair of the executive committee of the Socialist Party of Serbia, said: "The higher turnout today is a good thing for all Serbians, as it gives them a chance to decide their destiny."
Marko Blagojevic, a pollster from the CESID agency, told the BBC: "We've been monitoring today's turnout and it was 31% by the middle of the day. That's 2% higher than it was three years ago, so I expect the total turnout to be at least 60% by the end of the day.
"The higher turnout has been caused by civic organisations putting a lot of effort into raising awareness of how important the elections are. and the weather has also helped - it's been 20C."
