Anger over political corruption emerged as the unifying issue for the demonstrators, who vowed to stay in the streets until concrete steps are taken to reform the political system.
Across Brazil, protesters gathered to denounce legislation, known as PEC 37, that would limit the power of federal prosecutors to investigate crimes - which many fear would hinder attempts to jail corrupt politicians.
Federal prosecutors were behind the investigation into the biggest corruption case in Brazil's history, the so-called "mensalao" cash-for-votes scheme that came to light in 2005 and involved top aides of former President Luiz Inacio Lula da Silva buying off members of congress to vote for their legislation.
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Last year, the supreme court condemned two dozen people in connection with the case, which was hailed as a watershed moment in Brazil's fight against corruption. However, those condemned have yet to be jailed because of appeals, a delay that has enraged
Brazilians.
The protests continued despite a prime-time speech the night before from President Dilma Rousseff, a former leftist guerrilla who was tortured during Brazil's military dictatorship. She tried to appease demonstrators by reiterating that peaceful protests were a welcome, democratic action and emphasising that she would not condone corruption in her government.
The wave of protests began as opposition to transport fare rises became a laundry list of causes including anger at high taxes, poor services and high World Cup spending, before coalescing around the issue of rampant government corruption.
They have become the largest public demonstrations Latin America's biggest nation has seen in two decades.
Across Brazil, police estimated that about 60,000 demonstrators gathered in a central square in the city of Belo Horizonte, 30,000 shut down a main business avenue in Sao Paulo, and another 30,000 gathered in the city in southern Brazil where a nightclub fire
killed more than 240 mostly university students, deaths many argued could have been avoided with better government oversight of fire laws.
Thousands more protested in dozens of Brazilian cities.
In Belo Horizonte, police used tear gas and rubber bullets to disperse protesters. Salvador also saw protests turn violent.
During her pre-recorded TV speech, Rousseff promised that she would always battle corruption and that she would meet with peaceful protesters, governors and the mayors of big cities to create a national plan to improve urban transportation and use oil
royalties for investments in education.
But not all were convinced by her promises of action.
Victoria Villela, a 21-year-old university student who joined the crowd, said she was "frustrated and exhausted by the endless corruption of our government".
In the northeastern city of Salvador, where Brazil's national football team played Italy and won 4-2 in a Confederations Cup match, some 5000 protesters gathered about 5km from the stadium, shouting demands for better schools and transportation and
denouncing heavy spending on next year's World Cup.
