An estimated 1 million protesters took to the streets in more than 80 cities on Thursday night in the biggest show of anger yet against the government, which is being accused of corruption, high prices and a lack of investment in public services.
The worst confrontations unfolded late into the night in Rio de Janeiro, where more than 300,000 people protested in the city which is hosting key Confederations Cup games. Police fired tear gas and rubber bullets during battles through the streets.
But world football's governing body is pressing ahead with the eight-team Confederations Cup, which serves as a test event for the 2014 World Cup, in which 32 teams will be playing in the sport's showcase tournament.
When asked about the possibility of cancelling the Confederations Cup, FIFA said in a statement to The Associated Press: "To date, neither FIFA nor the LOC (local organizing committee) have ever discussed any such possibility."
Mass protests have been rare in recent years in Brazil, a country of 190 million people, but an outpouring of public anger has been mushrooming over the last week.
What started as demonstrations against increases in bus and subway fares in Sao Paulo and Rio de Janeiro have galvanized Brazilians to take their grievances to the streets, and led to a violent police crackdown.
Some protesters have denounced the billions of public dollars spent on stadiums in advance of the World Cup and the 2016 Olympics in Rio.
The government is projecting that $13.3 billion will be spent on stadiums, airport renovations and other projects for the World Cup, with an estimated $3.5 billion on venues.
"We want hospitals and schools in FIFA standards," read one banner outside the Maracana Stadium in Rio on Thursday ahead of Spain's match against Tahiti.
FIFA President Sepp Blatter has urged protesters not to "use football to make their demands heard."
Blatter surprised the Brazilian government by unexpectedly leaving Brazil this week to go to Turkey for the under-20s World Cup. Blatter is due back in Brazil next week for the semifinals and final of the Confederations Cup.
Rob Harris can be reached at http://twitter.com/RobHarris