Protesters massed in four Brazilian cities Monday in what they hoped would be their biggest demonstrations yet against a hike in public transport fares, stoking fears of more clashes with police and raising questions about security during big events like the current Confederations Cup and a papal visit next month.

With the nation's reputation on the line, authorities vowed to avoid the sort of bloody confrontations that shocked Sao Paulo last week. Police commanders said publicly they would not fire rubber bullets during the protest or use riot police units.

Authorities said they would respond with force only if protesters destroyed property.

On Thursday in Sao Paulo, riot police charged into crowds of peaceful protesters, firing rubber bullets and tear gas and beating some demonstrators. Protest organizers said more than 100 people were hurt. Police only confirmed about a dozen injuries.

Police used tear gas and rubber bullets again Sunday when several hundred protesters marched near Maracana stadium before a Confederations Cup match between Italy and Mexico, part of an eight-team warm-up tournament for next year's World Cup finals in Brazil.

But there were no clashes Monday as thousands of people protested before a Confederations Cup match between Tahiti and Nigeria in the city of Belo Horizonte, where police helicopters buzzed overhead and mounted officers patrolled the stadium area. Police put the number of protesters at around 20,000, according to a report on the G1 news website. Earlier in the day, demonstrators erected several barricades of burning tires on a nearby highway, disrupting traffic.

The protests were set off by a 10-cent hike in public transport fares, but they have clearly moved beyond that issue to tap into widespread frustration in Brazil about a heavy tax burden, politicians widely viewed as corrupt and woeful public education, health and transport systems.

Monday's protest in Sao Paulo got off to a calm start late in the day, with some demonstrators turning out in clown costumes complete with red rubber noses. Samba percussion circles, including one led by a drag queen in a blond wig and sporting oversized dollar-sign earrings, pounded out competing rhythms as the crowd of several hundred grew steadily thicker.

Demonstrator Marcos Lobo, a 45-year-old music producer, said earlier police brutality had persuaded him to come out for Monday's demonstration.

``I thought they (the protests) were infantile at first because of my preconceived notions,'' Lobo said. ``Then I saw the aggression.''

Another protester, Manoela Chiabai, said she came out to express her dissatisfaction with the status quo.

``Everything in Brazil is a mess. There is no education, health care _ no security. The government doesn't care,'' the 26-year-old photographer said. ``We're a rich country with a lot of potential but the money doesn't go to those who need it most.''

Demonstrations also were being held in the capital of Brasilia and in Rio de Janeiro. Thousands of protesters, many dressed in white and brandishing placards and banners, turned out in both cities. Many people in Rio left work early to avoid traffic jams downtown.

In Brasilia, several thousand people under heavy police escort marched on the Esplanada dos Ministerios thoroughfare that cuts between rows of government ministry buildings.

Ariadne Natal, a professor at the University of Sao Paulo whose research focuses on violence, said protesters want to ``take advantage of this moment when we have foreign visitors, when the world's press is watching, to showcase their cause.''

``The problem we've seen is that the police action is trying to prevent these protests,'' she said. ``What we need to figure out is how the protests as well as the big events can be carried out democratically.''

Brazilians have long accepted malfeasance as a cost of doing business, whether in business or receiving public services. Brazilian government loses more than $47 billion each year to undeclared tax revenue, vanished public money and other widespread corruption, according to the Federation of Industries of Sao Paulo business group.

But in the last decade, about 40 million Brazilians have moved into the middle class and they have begun to demand more from government. Many are angry that billions of dollars in public funds are being spent to host the 2014 World Cup and 2016 Olympics while few improvements are made elsewhere.

Protests are routine in Brazil, but few turn violent, and security experts say the demonstrations aren't the main danger for the hundreds of thousands of visitors who will descend on Brazil from now through the Olympics.

``The biggest threat to those visiting Brazil for the Confederations Cup and other events we'll host remains petty crime,'' said Paulo Storani, a security consultant and former commander of an elite police unit in Rio.

For the Confederations Cup, Brazilian officials are using drones, thermal cameras and thousands of troops to patrol the six stadiums hosting matches in six different cities.

Storani and other security experts said visitors will be most vulnerable once they venture away from secured areas, and may even face increased risks of petty crime because many police have been called off their regular patrols to focus on the stadiums and protests.

However, Joe Biundini, whose FAM International Group provides security details to executives attending the Confederations Cup, warned of the danger of escalating violence if the government doesn't negotiate with demonstrators.

``If the government doesn't sit down with them it could get worse in future matches,'' Biundini said, calling the police response to Sunday's protest in Rio excessive.

``It was a peaceful protest and they responded with a very heavy hand,'' he said. ``I'm a little concerned that the government of Rio is pulling out a heavy fist and that might just create more violence in the future.'' (AP)