Up to 20,000 people turned out after work in the country's biggest city, Sao Paulo, as well as a few thousand in Rio de Janeiro, demanding prison for former president Luiz Inacio Lula da Silva for corruption.
Thousands of Brazilians demonstrated in favour of prison for former president and election front runner Luiz Inacio Lula da Silva on the eve of a Supreme Court ruling on Wednesday on whether he should start serving a 12-year sentence for corruption.
Up to 20,000 people turned out after work in the country's biggest city, Sao Paulo, as well as a few thousand in Rio de Janeiro and smaller numbers in other cities.
Lula, 72, was sentenced to 12 years and one month in prison after being convicted last year of accepting a seaside apartment as a bribe from a huge construction company seeking government contracts.
He appealed in a lower court, but lost.
The head of the army, General Eduardo Villas Boas, tweeted that the military shared Brazilians' "desire for the repudiation of impunity."
Villas Boas also asked "who is really thinking about the good of the country and future generations and who is only worried about personal interests?"
The protesters demanded that Lula begin his sentence and be barred from the October 7 presidential election in which the veteran leftist is leading in the polls, despite his legal problems.
"We want Brazil to be freed of this shameful corruption. Imprison Lula and let Brazil turn the page," said Mara Massa, 67, at the protest in Sao Paulo, where the crowd chanted "No more Lula!"
São Paulo: protest in favor of #LavaJato corruption crackdown probe takes place; peaceful and in civilized fashion, people demand ex president Lula in Jail & push Supreme Court for more responsibility #Brazil #VemPraRua3deAbril pic.twitter.com/NDeQSfI9Ld— Rey Damy-Castro (@Rey_Brazil) April 3, 2018
Rallies in favour of Lula
Smaller demonstrations in favour of the Workers' Party founder also took place around the country.
The court showdown scheduled in the capital Brasilia on Wednesday has become a focal point for Brazil's deeply divided electorate.
Under current law, that means he should go immediately to prison, while pressing further appeals. However, Lula has asked the Supreme Court to grant him habeas corpus recourse, allowing him to remain free while pursuing those appeals.
The court is believed to be evenly split on the issue, so that one judge changing position would be enough to secure Lula's freedom – and boost his uphill bid for a third term in office.
If the court turns him down, he could face jail this week.
Attack on democracy
Those on the left who remember Lula for lifting tens of millions of people out of poverty during his two terms from 2003-2010 consider the threat of prison an attack on democracy.
Lula told a large crowd in Rio de Janeiro late on Monday that he saw his fight as a continuation of the struggle against a two-decade dictatorship that ended in 1985.
"I did not accept the military dictatorship and I will not accept this dictatorship of the prosecutors," he said.
Ahead of Villas Boas's unusual comments, an army reservist general lashed out in Estadao newspaper that a Supreme Court ruling that freed Lula would "induce" violence and "fratricidal conflict."
General Luiz Gonzaga Schroeder Lessa, who has a history of making provocative remarks, even appeared to threaten a coup, saying an eventual Lula election victory would "leave no recourse but an armed reaction. The armed forces would have to restore order."
Lula is not the only major Brazilian politician in trouble this week.
Current centre-right President Michel Temer, who already faces two corruption charges, is embroiled in new controversy following the arrests of several close associates on graft charges.
They were charged on Thursday in connection with the "Car Wash" probe into whether port logistics company Rodrimar was given contracts at Sao Paulo's huge Santos port after bribing Temer.
A third charge against Temer could be announced, although as long as he is in office he faces little risk of prosecution.