Demonstrators march in several cities to demand fair elections in October amid fears President Jair Bolsonaro would not accept the outcome if he loses the presidential vote.
Thousands of Brazilians have taken to the streets in a symbolic "defence of democracy" march after President Jair Bolsonaro's sustained attacks on democratic institutions just weeks ahead of elections.
Thursday's demonstrations in several cities were sparked by fears that the far-right leader, currently lagging behind in opinion polls, would not accept the outcome of October's vote given his repeated attempts to cast doubt on Brazil's electoral system.
"After 200 years of independence in Brazil, we should be thinking about our future... but we are focused on preventing a regression," University of Sao Paulo rector Carlos Gilberto Junior told a gathering of hundreds of academics, businessmen, trade union leaders and civil society members.
Outside the campus, thousands held up banners denouncing Bolsonaro and proclaiming: "Respect the vote, respect the people."
Some were dressed as electronic voting machines, which Bolsonaro claims, makes rigging the elections easier.
At the university gathering, a video was shown of Brazilian artists reading out a petition "in defence of the democratic state of law."
The petition has garnered more than 900,000 signatures since being posted online weeks ago.
Demonstrations were also held in Rio de Janeiro, Brasilia and Recife.
Voters in Brazil cast their ballots electronically at voting stations. But Bolsonaro has long argued for a paper printout to be made of each vote cast, suggesting the absence of a paper trail enables cheating.
He has not provided evidence of fraud, and the Superior Electoral Court insists the system is fair and transparent.
Violence feared if 'Brazil's Trump' loses
Last month, Bolsonaro repeated his claims at a meeting with foreign ambassadors, prompting the US embassy to later declare that Brazil's electoral system was a "model for the world."
His repeated attacks have led analysts to fear Bolsonaro may refuse to accept defeat like his former American counterpart Donald Trump, whose supporters stormed the US Capitol building after he lost the 2020 election to Joe Biden.
Several Brazilian business associations have also published open letters of concern, including the Brazilian Federation of Banks (Febraban) and the Federation of Industries of the State of Sao Paulo (Fiesp).
This is seen as a setback for Bolsonaro, who drew much support from the business sector in his 2018 election.
According to the latest opinion poll by the Datafolha Institute, published on July 28, Bolsonaro lags 18 points behind former leftist president Luiz Inacio Lula da Silva, who is the favourite to win the election.