Joyful cheers of "Let's go, Lula!" rose from the jubilant crowd again and again as Brazilians paraded down Sao Paulo's Paulista Avenue on Sunday, celebrating the leftist leader's improbable election win.

Thousands of people spilled onto the streets following President Luiz Inacio Lula da Silva's victory over his right-wing rival Flavio Bolsonaro.

Also read: Trump critic Lula wins reelection in Brazil, securing fourth presidential term

He received 51.8 percent of the votes compared to 48.2 percent for former president Jair Bolsonaro's son, who has refused to acknowledge the result.

"I feel so happy!" 43-year-old Anna Zanatta told AFP before bursting into tears of joy.

"Lula's victory represents many things for us: freedom, our democracy, our history," she said, waving a flag bearing the message "Antifascist Action."

Zanatta viewed a hypothetical Bolsonaro victory as a "threat" to Latin America's largest democracy.

"I was born under a dictatorship, and I promised my granddaughter that we Brazilians would never go through that again," she said, referring to the military regime which ruled from 1964 to 1985.

Doorman Alfonso dos Reis, 64, carried a sign reading "Lula again with the strength of the people" alongside a photo of the president.

"We're going to build a much better country," he beamed.

Fireworks boomed and cars honked their horns as the crowd marched down Sao Paulo's main avenue, which turned into a sea of yellow and green as the Brazilian flag covered every square inch of the place.

Also read: 'Brazil is no one's backyard': Re-elected Brazilian president Lula da Silva

Mateus Freitas, a 33-year-old theater actor, waved a flare that sent red smoke into the air, the color associated with Lula's Workers' Party (PT).

"No amnesty! No amnesty!" Freitas yelled at the top of his lungs.

He was referring to attempts to free Jair Bolsonaro, who governed from 2019 to 2022 and is serving a 27-year sentence for attempting a coup following his own electoral loss to Lula in 2022.

His son Flavio had promised to liberate him if elected.

"We stopped a government that would have been a fascist government, led by militias, criminals, racists, homophobes," Freitas told AFP.

"This is a victory for minorities, for the people, for Brazilian workers...Lula's government is inclusive," he said.

The leftist victory has swerved Brazil away from a rightward turn, unlike a recent string of wins championed by US President Donald Trump across Latin America.

Flavio Bolsonaro came out on top in the first round of presidential elections, and polls had given him a slight advantage ahead of the runoff.

Those indicators had concerned Felipe Rodrigues, a 53-year-old architect taking part in Sunday's celebrations.

"I'm very glad to see that, despite the risks of having a far-right government, which seems to be a global trend, here in Brazil we have a president who continues his efforts to improve the lives of the poor," he said.