Demonstrators take part in a protest against Brazil's President Jair Bolsonaro in Sao Paulo, Brazil, on Tuesday. Photo: VCG

President Jair Bolsonaro upped his attacks on perceived enemies including the Supreme Court and the electoral system Tuesday, vowing to defend supporters' "freedom" as Brazil marked its Independence Day with rival pro- and anti-government rallies.

Throngs of Bolsonaro supporters flooded streets with the green, yellow and blue of the national flag in Brasilia, Sao Paulo, Rio de Janeiro and other cities, holding massive prayer sessions and chanting slogans in support of the embattled far-right leader. Shouting "Get out, Bolsonaro," opposition protesters held their own rival rallies, an opening salvo ahead of elections in October 2022 that polls currently place the president on track to lose. 

Bolsonaro, whose popularity is at an all-time low, is seeking to fire up his base in the face of a flagging economy and a series of investigations targeting him and his inner circle.

Bolsonaro, a 66-year-old former army captain who is openly nostalgic for Brazil's military dictatorship (1964-1985), warned his backers their "democracy" and "freedom" were under threat by the powers that be in Brasilia.

"As of today, we're going to start writing a new history here in Brazil," he told the rally in the capital, where he kicked the day off with a flag-raising ceremony and Air Force flyover.

With hard-line backers urging a military intervention to give Bolsonaro unfettered power, there had been fears the day could turn violent, with echoes of the January 6 attack on the US Capitol by supporters of former president Donald Trump - to whom Bolsonaro is often compared.

Police reported few incidents, though Bolsonaro supporters harassed journalists covering the rallies in Brasilia and Sao Paulo, and tore down a police barricade in the capital Monday night. 

Bolsonaro doubled down on his attacks on Brazil's electronic voting system, telling a massive crowd in Sao Paulo he refused to take part in an election "farce" in 2022.

"We want clean, democratic elections... I can't participate in a farce like the one being sponsored by the Superior Electoral Tribunal," he said.

"Only God can remove me. I'm only coming out of this jailed, dead or victorious."

Bolsonaro has repeatedly attacked Brazil's voting system, claiming - without evidence -that it is plagued by fraud.