Brazilian President Jair Bolsonaro on Thursday backed his ally Donald Trump's claim of fraud in the US presidential election, and warned the chaos that rocked Washington could also hit Brazil's elections next year.

The far-right leader, dubbed the "Tropical Trump," is a staunch supporter of the American president, a stance he maintained even as international condemnation poured in for Trump's role in encouraging the mob that stormed the US Capitol Wednesday.

"What was the problem that caused that whole crisis, basically? Lack of trust in the election," Bolsonaro told supporters outside the presidential palace.

"They maximized mail-in ballots because of this pandemic thing, and there were people who voted three, four times. Dead people voted. It was a free-for-all. No one can deny that."

Election officials, US states and the courts have all dismissed Trump's claims of widespread fraud.

But Bolsonaro has shown determination to stand by Trump to the end.

Brazilian President Jair Bolsonaro is standing by his close ally Donald Trump, even after pro-Trump rioters stormed the US Congress Brazilian President Jair Bolsonaro is standing by his close ally Donald Trump, even after pro-Trump rioters stormed the US Congress Photo: AFP / EVARISTO SA

He was the last leader in the G20 group of nations to acknowledge president-elect Joe Biden's victory, which he did only after the US electoral college officially confirmed the November 3 election result more than a month later.

Political analysts say Trump's defeat isolates Bolsonaro, who modeled his own rise to the presidency on the Republican billionaire's, and hurts his chances for re-election in 2022.

As the shocking images of Wednesday's unrest in Washington circulated in Brazil, many commentators speculated the South American country could be headed for a similar situation next year if Bolsonaro loses.

"Trump just gave Bolsonaro his script for 2022," journalist Igor Gielow wrote in leading newspaper Folha de Sao Paulo.

Bolsonaro only fueled those concerns when he repeated his frequent criticism of Brazil's electronic voting system, which he alleges -- without evidence -- is riddled with fraud.

"There's fraud here, too," he said, warning Brazil faced "an even worse problem than the United States" if it did not reintroduce paper ballots, as he has insisted.