BELGRADE, SERBIA -- A preliminary official vote count Monday of Serbia's parliamentary election confirmed an overwhelming victory for populist President Aleksandar Vucic's right-wing governing party.

Election authorities said, after counting nearly 65% of the ballots, that Vucic's Serbian Progressive Party won around 61% of the vote, followed by his ally, the Socialists, with around 10%. They said turnout was 50.32%.

A partial boycott of the vote, by the main opposition parties who said Vucic unfairly dominated the state-run media, helped pave the way for Vucic's Progressives to control about 190 seats in the 250-member assembly. Vucic declared the party's victory as "historic."

International observers from the OSCE Office for Democratic Institutions and Human Rights said in a statement that "the election was characterized by intense political polarization, amidst a boycott by a considerable section of the opposition."

"The Serbian authorities organized the elections efficiently in difficult circumstances, but voters were left under-informed and frustrated by the opposition's lack of access to the media," said Urszula Gacek, head of ODIHR's special election assessment mission. "The dominance of the ruling party risks the neutrality of the country's democratic institutions, and dialogue is needed to bridge the deep political divisions and protect pluralism."

The autocratic Serbian president had called on supporters to vote in large numbers to give him a strong mandate for internationally mediated peace negotiations on the future of Serbia's former province of Kosovo. Serbia has rejected Kosovo's declaration of independence in 2008.

The European Union's envoy for Kosovo, Miroslav Lajcak, is expected in Belgrade later Monday to meet Vucic. The president travels next to Moscow, a key ally, and a U.S.-brokered Serbia-Kosovo meeting is set for June 27 in Washington.

Among the first to congratulate Vucic on Monday was a close populist ally, the prime minister of neighbouring Hungary, Viktor Orban, who said in a message that under Vucic's leadership, Serbia is ready, alongside other central European nations "to be a winner of the decade ahead of us."

"I am convinced that your successful governance has laid the groundwork for Serbia to become a full member of the European Union by the end of the four-year parliamentary cycle," Orban said.

Sunday's vote in Serbia was the first national election in Europe since the coronavirus lockdowns began. The voting -- initially planned for April but postponed because of the pandemic -- was held as Serbia still is reporting dozens of new cases daily.

Despite the partial boycott, some smaller parties still took part in the vote, but could not make it over the 3% threshold to get into parliament. Full official results are expected by Thursday.

Some opposition leaders alleged that the vote was marred by irregularities and intimidation of voters. An opposition mayor of the western town of Sabac said he will demand a repeat of the balloting, while one of the leaders of the pro-boycott bloc insisted the turnout was lower than officially stated.

"The boycott succeeded, the government will have no legitimicy," Dragan Djilas said in a statement.

A former extreme nationalist, Vucic briefly served as information minister in the government of late strongman Slobodan Milosevic during the bloody 1990s wars in the Balkans that killed more than 100,000 people and drove millions from their homes.

While Vucic now says he seeks EU membership for Serbia, critics warn that democratic freedoms have been sharply eroded since his party came to power in 2012.

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Associated Press writer Pablo Gorondi contributed from Budapest, Hungary