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

They were held under the shadow of a looming UN decision on the future of the breakaway southern province of Kosovo, whose ethnic Albanian majority is demanding independence following the 1998-1999 war there.

The leader of the Radicals (SRS), Tomislav Nikolic, claimed victory after official poll monitors said his party had garnered 28.7 percent of votes based on partial unofficial results.

The Center for Free Elections and Democracy (CeSID) said the Radicals were followed by the pro-European Democratic Party (DS) with 22.9 percent and the conservative Democratic Party of Serbia (DSS) with 16.7 percent.

"We have won as we had expected," Nikolic, the Radicals' candidate for prime minister, told AFP.

Pro-EU forces control majority

But Serbian President Boris Tadic said the polls were a breakthrough for pro-European Union forces, which he urged to form a coalition government as soon as possible.

"All parties supporting a pro-European stance won a majority and this is an important signal that Serbia will send to Europe and the world," said Tadic, the leader of the DS.

Tadic's Democrats are now being tipped to form a government with moderate nationalist Prime Minister Vojislav Kostunica's Democratic Party of Serbia and G17 Plus.

The three main groupings were followed by the reformist G17 Plus party with 6.8 percent, Milosevic's Socialist Party of Serbia with 5.9 percent and a neo-liberal alliance led by the Liberal Democratic Party (LDP) with 5.3 percent.

"It's necessary to form the government as soon as possible in order to start solving all problems that are awaiting us," said Tadic.

Nikolic, an outspoken critic of the UN administration in Kosovo, the European Union and international war crimes trials against Serbs, said he was "not convinced that we (the Radicals) will be able to form the government."

He earlier ruled out forming a government with major opponents and warned moderate parties would "surrender" Serbia's sovereignty over Kosovo.

Kosovo remains critical issue

Sunday's election came with Serbia on the brink of losing Kosovo, its historic heartland which has been run by the United Nations since the end of the 1998-1999 war between Serb forces and ethnic Albanian guerrillas.

UN envoy Martti Ahtisaari is expected to propose a form of independence for Kosovo next week, which the international community hopes will resolve the most sensitive issue left over from the bloody 1990s.

Ethnic Albanians, who comprise about 90 percent of Kosovo's two million people, are seeking independence, a demand staunchly opposed by Serbia which is willing to consider only a form of broad autonomy.

The UN envoy delayed his long-awaited proposal until after the polls so as not to inflame nationalist sentiment in Serbia at election time.

Asked by reporters whether he would accept Kosovo's independence, Tadic said: "Loud and clear, the answer is no."

And Kostunica, a fervent opponent of Kosovo's independence, is expected to fight to hold on to his position, possibly in a bid to delay the formation of a coalition government and impact on the Kosovo process.

Result to be confirmed Thursday

But he said his party was ready for talks on a new cabinet "as soon as final results are known," alluding to a Jan. 25 deadline for the electoral commission to confirm the vote outcome.

"What's more important is to have a consensus in the parliament ... especially when future status of Kosovo is in question," said Kostunica.

Kosovo was a central theme of election campaigning ahead of a United Nations decision next week on the future status of the breakaway province which has been run by a UN mission since its 1998-1999 war.

Serbians voted for 250 parliamentary deputies from 20 political groups. Kosovo Albanians are excluded from rolls, having boycotted Serbian elections since the early 1990s.

Some 500 international and 5,000 local observers monitored the vote.