BELGRADE, Serbia — Pro-European Union Democrats and Socialists reached an agreement on Wednesday to form a new coalition government in Serbia, after an election that indicated the bloc has kept its luster in the Balkans despite the eurozone crisis.

Top officials of the Democratic Party and Serbian Socialist officials reached the deal during a meeting, and the Socialists also agreed to support Democratic Party leader Boris Tadic in the runoff presidential vote on May 20 against populist candidate Tomislav Nikolic.

The new Serbian government would leave Nikolic's nationalist Serbian Progressive Party, which won the most votes in Sunday's parliamentary election, in the opposition.

Nikolic, who had claimed to have shifted from his staunchly anti-Western stance to a pro-EU one, was furious, and he returned to his trademark hardline rhetoric.

He accused Tadic on Wednesday of unspecified criminal links. "It is time for the citizens to see who they are dealing with," Nikolic said at a news conference.

He claimed that Serbia and its politicians have been "taken over by" criminals, but he provided no details or proof of his allegation.

Sunday's vote was rated free and fair by foreign observers.

The Socialists doubled their tally in the election compared to the previous one, achieving their best result since their founder Slobodan Milosevic was ousted from power in a pro-democracy uprising in 2000.

Nikolic's Progressives won 73 seats in the 250-member parliament, Tadic's Democrats took 67 seats and Ivica Dacic's Socialists won 44 seats. No party had enough to govern on its own.

The new government must be approved by Serbia's next parliament.

Senior Socialists official Milutin Mrkonjic said parties in the coalition, which also had formed Serbia's last government, were "logical" because they had won majority support from the voters.

Ivan Vejvoda, a political analyst at the German Marshall Fund, said that by supporting pro-EU parties, Serb voters had sent a twofold message.

"There is a sense of deep concern and dissatisfaction with the political class, but also of belief in the need to pursue the paths of democratic reform and European integration," he said. Serbia was granted an EU candidacy status in March, and hopes to get a date by the end of this year for the start entry negotiations.

Socialist leader Ivica Dacic had said he would seek to be prime minister in any future Serbian government, but the Democrats said in a statement Wednesday that details about the composition of the future Cabinet will be worked out after the presidential runoff.

Mrkonjic said Dacic will be "one of the candidates" for the post of prime minister.

Associated Press writer Jovana Gec contributed.