Serbia's election commission meets on May 12 to review allegations by the country's leading opposition party that recent elections were rigged.
The nationalist Serbian Progressive Party has accused authorities of forging 500,000 ballots in the May 6 presidential, parliamentary, and municipal polls.
The Progressives won the largest number of parliament seats in the poll but have been shut out of a coalition deal and say they been deprived of a wider margin of victory because of fraud.
Party leader Tomislav Nikolic, who finished a close second to the pro-European incumbent Boris Tadic in the presidential vote, will face his rival in a runoff on May 20.
Nikolic has called for the results of the May 6 polls to be annulled.
Local and Western monitors reported only minor violations during the vote.
Based on reporting by dpa and Tanjug