By Aleksandar Vasovic
BELGRADE (Reuters) - Serbia's main opposition party accused the dominant pro-Western Democratic Party on Thursday of stealing 500,000 votes in weekend elections and threatened to call supporters into the streets after an upcoming presidential run-off.
The opposition rightist Serbian Progressive Party (SNS) narrowly won a parliamentary election on Sunday but faces being locked out of government by a renewed coalition of the Democratic Party and its allies.
On the steps of parliament, SNS leader Tomislav Nikolic tipped what he described as thousands of unused ballot papers on the ground, saying they were found dumped in a garbage container, and accused the Democrats of adding the names of dead people to the voter list.
"We'll prove they stole 15 percent of the votes," Nikolic told reporters. "They took the names of 500,000 dead people and listed them as voters. The dead cannot complain."
The party had not lodged an official complaint but said it expected police to react. Nikolic threatened "magnificent" street protests.
The state Election Commission dismissed the accusations as unfounded. Nikolic goes head-to-head with incumbent president and Democratic Party leader Boris Tadic in a run-off for the presidency on May 20.
The accusations come a day after Tadic's Democratic Party announced it had reached a deal with the third-placed Socialists of late strongman Slobodan Milosevic to renew their 4-year-old governing coalition that would keep the country edging towards the European Union.
Monitors from the Organisation for Security and Cooperation in Europe (OSCE) commended the May 6 parliamentary and presidential elections as "open and competitive" but noted "some lack of transparency" in the compilation of the voter register.
Later on Thursday, some 2,000 supporters of the far-right Dveri party, which failed to cross the five-percent threshold to enter parliament, marched through central Belgrade chanting "They stole the elections!"
Asked about the possibility of election fraud, state Election Commission spokesman Miodrag Petrovic told the Beta news agency: "There's no substance to such claims."
Tadic, who beat Nikolic in the first-round presidential election by less than 1 percentage point, accused his rival of mud-slinging.
"They are trying to smear my name," he told a campaign rally in the southern town of Prokuplje. "But they've had mud streaming from their faces for the past 20 years."
Nikolic says he shares the goal of EU integration for the country of 7.3 million people.
But he has struggled to win over moderates wary of his past as an ultranationalist and one-time ally of Milosevic when Serbia was bombed by NATO during the 1999 war in Kosovo.
(Additional reporting and editing by Matt Robinson in Prokuplje; Editing by Michael Roddy)