Far-right incumbent Jair Bolsonaro and leftist challenger Luiz Inacio Lula da Silva traded jabs and insults as they squared off Sunday in their first-ever head-to-head debate, two weeks from Brazil's presidential runoff election.

Lula attacked Bolsonaro as a "little dictator" and the "king of fake news," drawing accusations of lying, corruption and a "disgraceful" record in return, as the rivals sparred in the first debate for their polarizing second-round showdown on October 30.

Front-runner Lula, the charismatic but tarnished ex-president (2003-2010) who is seeking a comeback at 76, was particularly fiery criticizing Bolsonaro over his handling of Covid-19, which has killed 687,000 people in Brazil, second only to the United States.

Attacking Bolsonaro over his resistance to buying vaccines and embrace of unproven medications such as hydroxychloroquine, Lula said the president "carries the weight of those deaths on his shoulders."

"Your negligence led to 680,000 people dying, when more than half could have been saved," the ex-metalworker said in his trademark gravelly voice.

Bolsonaro, 67, sought to shift the focus to the issue of corruption -- a weak spot for Lula, who was jailed in 2018 on controversial, since-overturned charges stemming from the investigation of a massive graft scheme centered on state-run oil company Petrobras.

"Your past is disgraceful... You did nothing for Brazil but stuff public money in your pockets and those of your friends," Bolsonaro said, calling Lula a "national shame."

"Lula, stop lying, it's bad for you at your age," said the ex-army captain at another point, simultaneously defending his own record and taking a shot at his rival's age.

Below the belt

Already bitter, divisive and full of mud-slinging, the campaign has if anything veered further into negative territory since the first-round vote.

Lula's camp in particular has embraced attack strategies once seen more on the far-right, scouring archive video footage of Bolsonaro and pouncing on unflattering quotes to try to link him to freemasonry and cannibalism, for example.

Their latest attack implied Bolsonaro was a pedophile, with Lula allies calling the president a "depraved criminal" and expressing "disgust" Saturday for comments he made on visiting a house last year where a group of underage Venezuelan girls were apparently working as prostitutes.

The head of Brazil's top electoral tribunal, Judge Alexandre de Moraes, ordered dozens of Lula-linked websites to remove attacks related to the Bolsonaro video, ruling Sunday the incumbent's comments had been taken out of context.

Arriving at the debate in Sao Paulo -- the first in which only Lula and Bolsonaro took part -- the president said the previous 24 hours had been "the most terrible of my life" because of the attacks.

Lula did not mention the issue during the debate, but wore a pin for an anti-child sex abuse campaign on his lapel.

The free-wheeling debate rules allowed the candidates to roam the stage and approach the cameras, which both did frequently -- though they rarely looked at each other, with the notable exception of one tense silence that Bolsonaro finally interrupted by putting his hand on Lula's shoulder with a smile.

As has been the case for much of the campaign, far more time was spent on personal attacks than substantive discussion.

"Policy proposals have lost their central role, and accusations have taken their place," political scientist Christopher Mendonca told AFP.

Are polls wrong again?

Bolsonaro, the vitriolic hardline conservative who took office in 2019, finished second in the first-round election on October 2 with 43 percent of the vote, to 48 percent for Lula.

But many opinion polls had put Lula's lead in the double digits.

Bolsonaro's stronger-than-expected performance has given him an aura of momentum heading into the runoff, and increased speculation over the possibility of another surprise in two weeks' time.

Lula has 53 percent of the vote heading into the runoff, to 47 percent for Bolsonaro, according to a poll released Friday by the Datafolha institute.