Serbian nationalists on Saturday called for nationwide street protests over alleged election fraud, fueling tensions before a presidential runoff vote.
Nationalist leader Tomislav Nikolic said the Serbian Progressive Party will start peaceful protests as of Sunday because "we don't recognize" parliamentary and local election results held last weekend.
Nikolic will face pro-European Union candidate and incumbent President Boris Tadic in a runoff presidential election on May 20. Tadic led Nikolic by half a percentage point in the first round, and is considered a favorite in the runoff.
Nikolic has accused Tadic's Democrats of rigging the general elections by printing extra ballots and tampering with voting lists. Tadic rejected the claims, saying Saturday that the call for street protests "is a call to destabilize the country."
Nikolic said he will decide Saturday whether to take part in the runoff after he listens "to the peoples' voice." He said he doubted that Tadic even received enough votes among 12 candidates to qualify for the runoff.
Election experts said Nikolic cannot legally withdraw from the race between the two rounds, and his name will remain on the ballot.
"Even if he (Nikolic) withdraws, voters will have the opportunity to give him the support," said Marko Blagojevic, of the independent Cesid vote monitoring group.
The runoff's result could affect Serbia's bid to join the EU, a bid led by Tadic. Serbia formally became a candidate for entry in March.
Foreign and domestic election observers have said that last Sunday's vote was generally free and fair. Serbia's state electoral commission rejected Nikolic's call for the repeat of the complete vote, saying the vote was regular.
Nikolic's populists won the parliamentary ballot, before Tadic's Democrats. But the third placed Socialists said they would form the next government with the democrats, locking Nikolic's party out of power.
"Even if I won the presidency, with whom would I cooperate? With the government that rigged the vote?" Nikolic asked.
Authorities said they would investigate Nikolic's fraud claims.