Klara Dobrev, candidate of the 'Democratic Coalition Party', is seen during the campaign closing session in Budapest, Hungary, on Sept 17, 2021. (ATTILA KISBENEDEK / AFP)

BUDAPEST - A 49-year-old lawyer who favors closer ties with the European Union pledged to unseat Viktor Orban as Hungary's prime minister, after she won the first round of a contest that will produce his challenger in an election next year.

Klara Dobrev, the leftist Democratic Coalition's candidate, won the first round of primary vote ahead of another leftist, Budapest mayor Gergely Karacsony, who also campaigned on a pro-European agenda.

In next year's parliamentary vote PM Viktor Orban will, for the first time since he came to power in 2010, face a united front of opposition parties that also includes the Socialists, the liberals and the formerly far-right - and now center-right - Jobbik

In next year's parliamentary vote Orban will, for the first time since he came to power in 2010, face a united front of opposition parties that also includes the Socialists, the liberals and the formerly far-right - and now center-right - Jobbik.

Opinion polls put Orban's nationalist Fidesz party and the opposition coalition neck and neck, raising the prospect of the tightest election in more than a decade.

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Orban and Fidesz have held office largely due to an election system that favors big parties, though Karacsony, 46, unexpectedly defeated the Fidesz candidate in the 2019 Budapest mayoral election.

Either Dobrev - who preliminary results showed won 34.8 percent of the votes in the primary - or Karacsony - with 27.3 percent - could yet win through to face Orban for leadership of the country next year.

Dressed in the blue and yellow colors of the EU, Dobrev said at a news conference late on Thursday that, after a fair race, she was ready for the second round.

"We will not stop until we defeat Viktor Orban and his regime," Dobrev said, a vice-president of the European Parliament who has pledged to reduce poverty and work for adoption of the euro.

Karacsony has promised a more just tax system and to heal political divisions.

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Conservative Peter Marki-Zay, mayor of a southern Hungarian city, was in third place with 20.4 percent in the primary, for which opposition voters turned out in higher-than-expected numbers, with more than 633,000 people casting votes nationwide.

There will be a runoff next month among possibly the three top vote-getters.

While Dobrev leads now, it is not clear whom Marki-Zay would back in the second round if he decided to step down.

Dobrev is also the candidate of a party led by her husband, former Prime Minister Ferenc Gyurcsany, a deeply divisive figure who admitted in 2006 in a leaked speech that he lied about the economy to win national elections.

Orban has portrayed the opposition, especially Karacsony and Dobrev, as puppets of Gyurcsany.