Serbian nationalists are accusing the ruling Democratic Party of fraud in Sunday's presidential election.

Tomislav Nikolic, who heads the opposition Progressive Party, alleged Thursday that the Democrats printed extra ballots for ballot stuffing, discarded ballots and tampered with voting lists.

Mr. Nikolic faces incumbent Boris Tadic in a runoff election on May 20. Mr. Tadic came out slightly ahead of his challenger, but neither candidate garnered even 30 percent of the vote. A majority is necessary to win the election.

Mr. Tadic, who struck a deal this week with the third-placed Socialists to form a coalition government, has rejected the fraud claims.