Brazil's Jair Bolsonaro officially launched his presidential re-election campaign on Sunday, attacking the voting system, the judiciary and his main challenger in a bellicose speech in Rio de Janeiro.

In a more than hour-long address at a sports arena, the far-right leader promised he would maintain a temporary social support grant if re-elected, and warned he would "not allow fraud" in the October vote -- a criticism of the electoral system he has repeatedly claimed, without evidence, is flawed.

Earlier this week, the US embassy in Brazil said the country's electoral system was a "model for the world" after Bolsonaro warned in an address to ambassadors that the system's "flaws" engendered "mistrust."

Such attacks in recent months have led analysts to fear that Bolsonaro -- who has been dubbed "Tropical Trump -- may refuse to accept defeat like his former American counterpart, whose supporters stormed the US Capitol after he lost the 2020 election to Joe Biden.

The event was held under strict security
The event was held under strict security AFP / MAURO PIMENTEL

Bolsonaro's repeated questioning of the electoral system has prompted the Supreme Court to open an investigation into him.

On Sunday, the president urged his supporters to take to the streets on September -- the one-year anniversary of independence day protests marked by attacks on democratic institutions that Bolsonaro had encouraged.

"The deaf and black-cloaked few have to understand the voice of the people," he said in reference to the Supreme Court. They "have to understand that it is the executive and legislative power that makes the rules."

Brazil’s President Jair Bolsonaro attacked the electoral system, judicary and his main rival
Brazil’s President Jair Bolsonaro attacked the electoral system, judicary and his main rival AFP / MAURO PIMENTEL

His supporters replied: "The people are supreme!"

They waved banners with slogans such as "God, Homeland and Family." One featured an image of Trump.

Changing the topic to his main rival and poll frontrunner -- leftist former president Luis Inacio Lula da Silva -- Bolsonaro said he prayed "that Brazil will never experience the pains of communism."

"We have to attract the young leftists to our side, show them the truth," he said.

"Where their candidate supported others in South America, look at the misery in those countries," said Bolsonaro, referencing Venezuela among others.

The crowd responded: "Lula, thief, your place is in prison!"

Bolsonaro appeared on stage with his wife Michelle and running mate Walter Souza Braga Netto, and wore a bullet-resistant vest under his shirt.

Amid fears for the safety of presidential candidates, the event was held under strict security with metal detectors at the entrance.

A month before the election he won in 2018, Bolsonaro was stabbed in the stomach at a campaign rally.

The last Datafolha poll in June showed Lula in the lead with 47 percent, followed by 28 percent for Bolsonaro.