Protests rocked the Confederations Cup on Friday as activists set fire to mounds of tires, blocking the entrance of Brasilia's Estádio Nacional Mane Garrincha.

Several hundred protesters surrounded police and local firefighters to prevent them from extinguishing the blaze, which sent plumes of thick black smoke high above the national stadium. There were no apparent casualties or injuries.

The Confederations Cup is scheduled to kick off on Saturday afternoon with Brazil hosting Asian champions Japan. The protests are not expected to derail either the opening ceremonies or Saturday's game.

The group, identifying itself as the Front for Urban Resistance (ANCOP) in a written statement given to FOX Sports, claimed that it is undertaking 12 other actions across Brazil on Friday at World Cup sites. That claim could not be independently verified; however, other protests took place overnight in Rio de Janeiro and Sao Paulo, and a security alert was issued on Friday advising travelers to avoid major transportation hubs in those cities.

A spokesman for the group, who identified himself to FOX Sports only as "Francisco," said his group was protesting the massive amounts of public money being spent on the World Cup by the Brazilian government, and listed a series of grievances.

"[The government] is treating us like terrorists," said Francisco. "We are not, we are Brazilians. They have spent millions, billions on the World Cup and nothing on the women and children and residents here."

Protests have been on the rise in Brazil as the World Cup approaches, with allegations of corruption and indifference to the plight of ordinary Brazilians at the fore. Some of the protests have turned violent. Fifty-five people were reported injured in Sao Paolo on Thursday as members of another group, the Free Pass Movement, clashed with police in a protest over transportation fare hikes. Police used rubber bullets and tear gas to clear the group and the center of the Sao Paolo was shut down for a short time. Another 2,000 people were reported to have marched in Rio de Janeiro as well.

Brazil has been struggling to reconcile the massive expenditures on World Cup infrastructure with a country which until recently had a quarter of the population living under the poverty line. Massive shantytowns line Rio and other major cities and income inequality remains a stubborn problem in what is the world's sixth-largest economy.

In their written grievances, ANCOP pointed to the half-billion dollars reportedly spent on Brasilia's Garrincha Stadium as well as the dislocation of residents to make way for what it termed "megaprojects."

FIFA has already made it clear that Brazil will have to do a better job for the World Cup, when the expectations will be much higher and the number of visitors will increase significantly compared to the eight-team Confederations Cup.

The Brazilians said FIFA should not worry about the delivery of the remaining six stadiums being built for the World Cup.

''This first delivery was actually the hardest deadline to meet,'' Brazil Sports Minister Aldo Rebelo said on a conference call this week. ''The evolution of the construction work of these (World Cup) stadiums ... indicates that, yes, they can and will be delivered in December (2013). We have been in close contact with the responsible parties for these stadiums to make sure that those deadlines are fulfilled.''

The government said infrastructure projects which were not ready in time for the Confederations Cup will also be finalized by the World Cup.

''We have been monitoring transportation and urban mobility on a daily basis,'' Rebelo said. ''These works will be delivered in time, together with the next six stadiums. Airport, security, telecommunications and urban mobility will be ready and compatible with the expectations held by the country and by the world.''

Asked about the protests, FIFA spokesman Pekka Odriozola said Friday that ''we are monitoring the situation and we are in touch with the local authorities.'' But he insisted that FIFA has ''full confidence and trust in the local authorities'' to cope with ''any circumstance.''

FIFA president Sepp Blatter also remained optimistic of Brazil's plans to produce a memorable experience for fans by offering his support on Twitter.

"Based on my tournament organisation experience, I'm confident with the #confeds logistical preparations," said Blatter.

Based on my tournament organisation experience, i'm confident with the #confeds logistical preparations. http://t.co/gkGHJd8Fan

-- Joseph S Blatter (@SeppBlatter) June 13, 2013 The Associated Press was used in this report.