Sparks flew Sunday as far-right President Jair Bolsonaro accused leftist rival Luiz Inacio Lula da Silva of massive corruption -- and drew accusations of "destroying Brazil" in return -- as they faced off in their first election debate.

The two front-runners, who waited until the last minute to confirm they would attend the first televised debate ahead of October's elections, wasted no time in attacking each other.

Bolsonaro called Lula a "thief" in his opening salvo of the three-hour clash, pummeling the 76-year-old ex-president over the massive "Car Wash" corruption scandal centered on state-run oil giant Petrobras.

The investigation landed Lula in prison from 2018 to 2019 on controversial corruption charges -- annulled by the Supreme Court last year.

"Your government was the most corrupt in Brazilian history," said Bolsonaro, 67, rattling off figures from the scandal in a rapid-fire attack.

"It was a kleptocracy, a government based on robbery.... What do you want to come back to power for? To do the same thing to Petrobras again?"

Lula fired back that Bolsonaro was spreading "untruths" -- one of several exchanges in which they accused each other of lying. He in turn accused the incumbent of trashing his legacy of economic growth and anti-poverty initiatives.

"This country has been destroyed," Lula said in his trademark gravelly voice, attacking Bolsonaro over increased poverty and hunger, soaring prices and a surge in destruction in the Amazon rainforest.

Dressing the part in dark suits and ties -- striped blue for Bolsonaro, burgundy red for Lula -- the front-runners had numerous fiery exchanges, but hewed to the rules and kept their demeanor relatively civilized.

However, tension erupted into the open in the side room where their entourages were watching. Pro-Lula lawmaker Andre Janones and Bolsonaro's ex-environment minister, Ricardo Salles, got into a raucous shouting match and had to be pulled away from each other.

Bolsonaro rants, Lula underwhelms

In all, six of the 12 presidential candidates on the ballot were on the neon-blue-lit stage in TV network Band's Sao Paulo studios.

But all eyes in the deeply polarized Latin American giant of 213 million people were on front-runner Lula, the popular but tarnished ex-metal worker who led Brazil from 2003 to 2010, and his nemesis, Bolsonaro, the leader nicknamed the "Tropical Trump," who is vying for a come-from-behind win.

Neither appeared to score a knock-out punch, and both drew criticism over their performances.

Bolsonaro sparked outrage with a trademark rant in which he attacked journalist Vera Magalhaes, one of the moderators, for saying he had spread disinformation about Covid-19 vaccines.

"Vera, you think about me in your sleep, you must have a crush on me or something," the incumbent reacted irately.

"You can't take part in a debate like this and spread lies and accusations about me. You're an embarrassment to Brazilian journalism."

The president, who has been struggling to win over women voters, drew accusations of misogyny on social networks after the episode.

Lula meanwhile delivered an underwhelming performance, looking less fiery as the three-hour debate wore on.

"Lula looked very timid and made mistakes on certain points, falling into some traps," said political analyst Andre Cesar of consulting firm Hold.

He gave Bolsonaro the edge in the debate for hitting on his favorite themes, "nation, family and freedom... often with humor." But he added the incumbent's attack on the moderator "showed that this is who Bolsonaro is -- and that might hurt him anyway."

Lula leads Bolsonaro by 47 percent to 32 percent, according to the latest poll from the Datafolha institute.

If no candidate wins more than 50 percent of valid votes in the first round on October 2, the election will go to a run-off on October 30.