President Luiz Inacio Lula da Silva and Senator Flavio Bolsonaro clashed during a heated debate ahead of the October 25 run-off vote. The leaders exchanged insults over the economy and US ties. "It is striking how the Bolsonaro family is subservient to American interests," said Lula during the tense broadcast.

Ahead of the run-off vote for the presidential elections in Brazil, incumbent President Luiz Inacio Lula da Silva and right-wing Senator Flavio Bolsonaro clashed over a series of topics, which later turned into personal attacks, marking their first debate.

The two leaders exchanged barbs, accusations and insults in a tense broadcast on Band TV that lasted about two hours, days before the October 25 vote.

In the first round of voting on 4 October, Flávio Bolsonaro, son of former president Jair Bolsonaro, won by 47 percent to Lula's 45 per cent.

The debate between Lula and Bolsonaro focused on the economy, public security, corruption and Brazil's relations with the United States, covering a range of issues which the voters of Brazil feel will impact the direction their country goes after the vote.

45-year-old Bolsonaro criticised Lula over the cost of living, public security and social spending, accusing the incumbent of spending recklessly to secure a fourth consecutive term.

Meanwhile, 80-year-old Lula targeted Bolsonaro over the senator's ties to US President Donald Trump.

"It is striking how the Bolsonaro family is subservient to American interests," said Lula, accusing the right-wing leader of conspiring to "hand over" Brazil's rare earth minerals to Washington.

However, as the debate went on, the attacks between the presidential candidates turned personal. With Lula calling Bolsonaro a "habitual liar and thug" for his alleged ties to Rio de Janeiro's paramilitary groups, and Bolsonaro saying he will keep Lula at a distance "because he may steal his wallet."

"Lying is the Bolsonaro family's strong suit," Lula said.

The younger Bolsonaro also called the incumbent a "clown" after dodging a question about a corruption investigation regarding his father, Jair Bolsonaro.

Jair Bolsonaro has been under house arrest while serving a 27-year sentence connected to efforts to overturn the 2022 election, which he lost to Lula.

The senator also told Lula that "Brazil is going to retire you."

As the debate heated up, Lula also battled to control his irritation at times and repeatedly asked viewers to "look it up on Google" to prove his adversary was lying.

Lula's attacks on Bolsonaro also come after Brazil's federal police asked the country's Supreme Court to open an investigation against Flávio over a money laundering accusation involving a lawyer close to him.

This case comes as the 45-year-old is already under investigation for his links to Daniel Vorcaro, a disgraced former banker who financed a movie about Jair Bolsonaro. The younger Bolsonaro has denied any wrongdoing.

Meanwhile, tens of thousands of supporters for the candidates took to the streets of Sao Paulo, Rio de Janeiro and other cities to rally for their leaders.

Pro-Bolsonaro crowds wearing Brazil's national colours of yellow, green and blue packed Paulista Avenue in Sao Paulo's financial centre.

Meanwhile, Lula supporters wearing red, symbolic of his Workers' Party, filled Brasilia's plaza of government buildings, while students backing the president protested against Bolsonaro in Rio de Janeiro.

The second debate between Lula and Bolsonaro is set for October 23 on TV Globo.