Brazilian authorities braced for new mass protests Thursday as a street revolt against government corruption and wasteful World Cup spending gained steam despite official concessions.

Hundreds of thousands of people in 80 cities responded to postings on Facebook, Twitter and Instagram calling for street rallies to demand better living conditions and slam the huge costs of hosting the 2014 World Cup.

On Wednesday, the protesters scored a major victory when authorities in Sao Paulo and Rio, Brazil's two biggest cities, canceled the transit fare hikes that had been the initial spark for two weeks of nationwide protests.

But the fare roll back was not enough to placate the crowds.

Later the same night, riot police fired tear gas to break up a mob of several hundred that tried to block a 15-kilometer bridge across the Guanabara Bay that links Rio with the nearby city of Niteroi.

The mob, which had earlier ransacked a bank branch, knocked over a bus then built barricades with debris and set them on fire.

There were also clashes between protesters and police in the northeastern city of Fortaleza near the stadium where Brazil beat Mexico 2-0 in their second Confederations Cup match and qualified for the semi-finals.

The popular revolt has evoked comparisons with the Arab Spring, the Occupy movement and the latest unrest in Turkey.

And there is no signs that the movement, which has no political coloration and no clearly identified leadership, is about to lose steam.

Initially ignited by the fare increases, the protest fed on widespread resentment at the billions of dollars the government is spending on the Confederations Cup, the World Cup and the 2016 Summer Olympics.

The demonstrators instead want higher funding for education and health and a cut in salaries of public officials. They are also railing against what they viewed as rampant corruption within the political class.

The protests are the subject of lively exchanges on social media.

"The fare increases were canceled. But who says we are going to stop?" wrote one subscriber.

Under the slogan "It's more than just 20 cents" -- a reference to the bus fare hikes -- Internet users organized new protests.

Those opposing the hosting of the World Cup are also planning a mammoth march to Rio's iconic Maracana stadium on June 30, the day of the final of the Confederations Cup.

Monday's rallies, when more than 250,000 people marched in several cities. were Brazil's biggest such mass demonstrations in 20 years.

That came as a surprise in a country rarely inclined to protest, particularly after a decade of social progress in terms of income and employment.

"It's a first step to show that we are not a dead people," said 24-year-old businessman Bruno Pastan, who stormed the roof of Brasilia's National Congress with 200 fellow protesters on Monday night.

Meanwhile police tightened security around the Congress building in Brasilia to prevent a repetition of Monday's disturbances

"Our concern is to avoid acts of vandalism," Agencia Brasil quoted Pedro Carvalho, had of the Senate police as saying.

"We have to respect the demonstrators, but I hope that things will not get out of hand," Renan Calheiros, the Senate speaker, said.

And Andre Vargas, the acting president of the Chamber of Deputies, announced that measures would be taken to protect public property.

"Demonstrating is a festival of democracy, but it must be peaceful and serene," he said, warning against any fresh occupation of the congressional building roof.