Rio de Janeiro (AFP) - Polarizing far-right politician Jair Bolsonaro easily won the first round of Brazil's presidential election on Sunday, but charged that "polling problems" cheated him of outright victory, forcing a run-off against a leftist rival in three weeks.

Bolsonaro, a 63-year-old former paratrooper vowing to crush crime in Latin America's biggest nation, received 46 percent of ballots -- below the 50-percent-plus-one-vote threshold required for a first-round win, according to an official count of virtually all votes.

That means he will have to duke it out on October 28 with left-wing candidate Fernando Haddad, who came in second at 29 percent.

Haddad, the former mayor of Sao Paulo who replaced jailed former president Luiz Inacio Lula da Silva in the contest, is seen as running neck-and-neck with Bolsonaro in the second round, surveys show.

Bolsonaro's supporters protested the results outside the national electoral tribunal in the capital Brasilia, chanting "Fraud!"

Other Bolsonaro voters expressed their bitterness, even though the result was close to pollsters' predictions.

"We expected to win in the first round," 77-year-old retiree Lourdes Azevedo said in Rio de Janeiro.

"Now things are more difficult: the second round is a risk."

Haddad, addressing his own supporters, called the looming run-off "a golden opportunity," and challenged Bolsonaro to a debate.

- A divided electorate -

Despite his complaints, Bolsonaro did not formally contest Sunday's result, saying his voters "remain mobilized" for the second round.

But he faces fierce resistance going forward from a big part of Brazil's 147-million-strong electorate, who are put off by his record of denigrating comments against women, gays and the poor.

His unabashed nostalgia for the brutal military dictatorship that ruled Brazil between 1964 and 1985 has sent a chill through many voters.

Haddad, though, has his own challenge.

As the Workers' Party candidate, he bears the palpable disappointment and anger of voters who blame the party for Brazil's worst-ever recession, and for a long string of graft scandals.

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Lula was disqualified from running due to his corruption conviction.

Sunday's general election -- in which new federal and state legislatures were also chosen -- exposed the deep divisions generated by both candidates.

Some voters -- particularly women -- carried "Not Him" placards to polling stations in opposition to Bolsonaro.

But his supporters, like 53-year-old lawyer Roseli Milhomem in Brasilia, said they backed the veteran lawmaker because "Brazil wants change."

"We've had enough of corruption. Our country is wealthy -- it can't fall into the wrong hands," she said.

Political analyst Fernando Meireles of Minas Gerais Federal University said momentum appeared to favor Bolsonaro.

"The probability of Bolsonaro coming out victorious seems pretty big right now," Meireles told AFP.

"It looks difficult for Haddad to win in the second round, but not impossible."

A Haddad voter, Jose Dias, said it would be a "catastrophe" if Bolsonaro won the right to succeed unpopular outgoing center-right President Michel Temer.

"A lot of young people are voting for him. They don't know what it was like under the dictatorship," he said.

- In Trump's mold -

Better-off Brazilians have rallied to Bolsonaro's pledge to crush crime in a country where there are more than 62,000 murders each year, nearly as many rapes, and frequent muggings and robberies.

Bolsonaro wants to boost police forces and relax gun laws for "good" citizens.

Many voters also like his promises to tackle corruption and to cut climbing public debt through privatizations, as well as the devout Catholic's family-first stance.

But poorer Brazilians, who benefited most from the heyday during Lula's time in office from 2003 to 2010, want a return to good times and hope Haddad can deliver.

The result is a very split electorate. Whoever ultimately wins the presidency in the world's eighth largest economy will grapple with a large bloc of ideological hostility.

Despite sitting in congress for nearly three decades, Bolsonaro casts himself as a political outsider in the mold of America's Donald Trump or the Philippines' Rodrigo Duterte: tough-talking, brash, and promising a root-and-branch overhaul to an electorate weary of traditional parties spouting empty promises.

Temer -- who took over after Lula's chosen successor Dilma Rousseff was impeached and ousted in 2016 for financial wrongdoing -- was not standing for re-election.

He will leave office at the end of the year as a deeply unpopular figure in a country with 13 million unemployed, climbing public debt and inflation, and record violence.