The 62-year-old Nikolic was deputy prime minister under the so-called "butcher of the Balkans" Slobodan Milosevic. In the post-war years, he ran the far-right Serbian Radical Party together with Vojislav Seselj - currently on trial for war crimes - before re-branding himself as pro-European.

He said after his victory on Sunday that: "Serbia will not walk away from its path to the EU."

But his campaign focused on the Serbian economy and quality of life rather than its EU prospects.

Serbia is suffering from high sovereign debt, corruption, 24 percent unemployment and low wages, with average monthly salaries at around €400. Nikolic pledged to increase taxes on the rich to help pay for social benefits and pensions and to invest in agriculture and industry.

"These elections were not whether about Serbia will go to EU, they were about solving problems that [Tadic's] Democratic Party has created in Serbia," he said.

For his part, Tadic lost the vote despite succesfully steering Serbia to EU candidate status earlier this year.

Widely endorsed by EU leaders in the run-up to Sunday's vote, he gained the EU status at the cost of normalising relations with breakaway Kosovo and delivering two Serb war crimes fugitives, Ratko Mladic and Radovan Karadzic, to join Nikolic's former ally Seselj in The Hague.

Nikolic's Serbian Progressive Party also won parliamentary elections on 6 May and aims to form a ruling coalition with the Socialist Party, led by Milosevic's wartime spokesman Ivica Dacic.

Meanwhile, top EU officials Herman Van Rompuy and Jose Manuel Barroso messed up their reaction to Sunday's vote.

The pair first congratulated Nikolic three hours before polls closed and six hours before the official result, raising concerns that their remarks might have influenced the vote. They retracted the message shortly afterward and published a new communique on Monday, with a European Commission spokesman calling the whole business a "technical mistake."

A senior Western diplomat based in Pristina previously told EUobserver that Nikolic is disliked in Brussels and Washington. "Nobody takes him seriously," the source said in an interview late last year.

Update: this story was amended at 12.30 Brussels time on 21 May to include the latest information on the EU statement gaffe