Taking advantage of unseasonably warm winter weather, voters began trickling in to some of the more than 8,500 polling stations across the Balkan nation, including Serbs in ethnic-Albanian dominated Kosovo.

Serbia's 6.6 million electorate, which excludes ethnic Albanians in its disputed southern province, is voting for 250 parliamentary deputies from 20 political groups.

Serbia's EU membership hopes at stake

At stake is Serbia's hope of eventual European Union membership, which hinges on Belgrade's war crimes cooperation, namely by capturing former Bosnian Serb general Ratko Mladic, who is wanted for genocide.

Brussels froze talks on closer ties last year and said it would restart them only when Mladic was on trial.

Some Western officials accuse hardline nationalists in Serbia's military and police of helping Mladic to hide and evade trial by the U.N. war crimes tribunal in The Hague.

"We sincerely hope the voters will turn out in large numbers and choose a European future for their country," said British ambassador Steven Wordsworth.

German ambassador Andreas Zobel said the elections "are of an extraordinary importance because they will determine the direction in which Serbia wishes to develop."

The parliamentary elections come the year after the death of former autocratic president Slobodan Milosevic and the independence of Serbia's traditional partner Montenegro in a historic referendum.

"Uncertain" outcome

The decisive race is expected to be between President Boris Tadic's reformist Democratic Party (DS), the ultra-nationalist Serbian Radical Party (SRS), and conservative Prime Minister Vojislav Kostunica's Democratic Party of Serbia (DSS).

"These elections are a turning point between the past, old-fashioned, traditional and incapable politics and a strategy which solves problems ... and leads Serbia to the EU," Tadic said during campaigning.

Official poll monitors, the Centre for Free Elections and Democracy (CeSID), said they believed the outcome of the election was one of the most "uncertain" in the country's history.

"There are some 250,000 new voters (since 2003 elections) and their ballots can be decisive as they are expected to vote for reformist forces," the head of CeSID, Zoran Lucic, said ahead of voting.

Opinion polls have shown none of the three leading parties are likely to win enough votes to form a government alone, with Tadic and Kostunica widely expected to put old differences behind them and join ranks in a coalition.

Fate of Kosovo

The election is set to have a strong bearing on Kosovo, the UN-run province of Serbia that remains the most sensitive issue left over from the bloody 1990s breakup of the former Yugoslavia.

It comes just five days ahead of the presentation of UN envoy Martti Ahtisaari's plans for the status of Kosovo, the ethnic-Albanian majority province of Serbia that has been run by the United Nations since 1999.

Ahtisaari, who led nine months of mostly fruitless talks between Belgrade and Pristina last year, chose to present his plans after the poll for fear it could boost the ultra-nationalists.

German Chancellor Angela Merkel, whose country heads the EU's six-month rotating presidency, said in an interview with news agency Reuters this week that any decision on Kosovo must bring "maximum" satisfaction to the citizens of the province without stirring unrest in Serbia.

"We need maximum satisfaction in Kosovo but also satisfaction, or at least no turbulence, in Serbia," Merkel said ahead of Sunday's Serbian elections. "First we want to see the democratic powers in Serbia strengthened after the election and then we will do everything we can to negotiate astutely while still moving ahead with political decisions."

Ethnic Albanians, who comprise about 90 percent of Kosovo's two million people, want nothing less than independence, a demand Belgrade staunchly opposes, instead offering them wide autonomy.

The major parties say they will not accept the loss of Kosovo, but the Democratic Party of President Boris Tadic -- the party favored by the West -- has come closest to telling Serbs that it might be inevitable.

Jaded voters

Despite the importance of the poll, a large number of voters are expected to abstain, fed up with politics and Serbia's protracted transition from communism, which has been delayed by the wars of the 1990s and their aftermath.

More than six years since the ouster of former strongman Milosevic, the impoverished country lags behind its neighbours with an average monthly salary of about 250 euros ($320) and about one million unemployed.

Some 500 international and 5,000 local observers were monitoring the vote. Unofficial preliminary results were expected late Sunday, while the final outcome is to be presented by January 25.