On Sunday night, as 75,000 people streamed into Rio de Janeiro's iconic Maracana Stadium for the first World Cup game to be played there since 1950, another crowd, of just 200, gathered a mile away. Wilson Ventura Jr. took his place among them: He has been a fixture for a year at protests against the Cup and what he sees as misspent Brazilian funds.

Before long police launched themselves into the crowd and he took off running, hands over his face to block out tear gas – but not soon enough. He was hit in the hand with a rubber bullet that sliced his finger open to the bone. And so Mr. Ventura made his second trip to hospital. Just three days earlier, when the Cup opened on Thursday, the 42-year-old systems analyst was beaten to a bloody pulp by eight to 10 police officers at another small Rio demonstration.

Mr. Ventura might almost have predicted he would end up hurt: The aggressive response by Brazilian police to small demonstrations is emerging as one of the major stories in an event that is otherwise unrolling without problems.

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"We have very violent police without a lot of experience in containing massive demonstrations, but these haven't been massive at all," said Ignacio Cano, an expert on public security with the State University of Rio de Janeiro. "They tend to overreact even when the demonstrators are not very close [to any sensitive area], and the reaction of police is making things worse. From a local point of view, demonstrations are very tiny, but if you read the international press you get a different impression – the police haven't been acting very wisely."

Before the start of this World Cup, the potential for large-scale protests to disrupt the tournament was one of the top fears of FIFA and the Brazilian government (and citizens anxious to show off their country, or just see some football).

A year ago, when Brazil hosted the Confederations Cup, the warm-up to FIFA's premier event, more than one million people came into the streets on a single day in the largest demonstrations this country had seen in a generation. They were protesting government corruption, poor public transport, the high cost of living, spending on the World Cup – a whole list of grievances. Smaller protests since then – with the slogan "Nao Vai Ter Copa," ("There won't be a Cup") – have gone on across the country.

But now that the games have arrived, police and journalists consistently outnumber protesters, and the gatherings are held miles from a location where they might disrupt the football matches.

This has not, however, prevented police from responding harshly: The desire of a sensitive Brazilian government to pull off a successful Cup (and justify the $17-billion (U.S.) spent to host it) seems to be pushing it to quell protests at any cost, rather than reaping the public-relations win in being seen to allow dissent.

At the demonstration where Mr. Ventura was hurt, two police officers were filmed firing live ammunition towards the crowd (no one was hit.)

As the tournament began in Sao Paulo on Thursday, police who were being recorded by a dozen journalists shot one demonstrator twice with rubber bullets, and after he was subdued, blasted his face with pepper spray from about 10 centimetres away. Fernando Grella, the minister for public security in the state, told reporters the pepper spray incident was "only a moment and we need to see the whole context," and that there will be an investigation.

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At the same demonstration, a correspondent and producer from CNN were hit with stun grenades and shrapnel; the producer has had surgery on her wound and the incident received considerable international attention. The governor, Geraldo Alckmin, said police "acted appropriately" during the protest and "avoided a bigger problem … Imagine the consequences if the police hadn't reacted and had allowed them to occupy [the major highway leading to the stadium] and the metro stations, while 80,000 people were trying to get to the stadium. If the police didn't act forcefully, this could have had bigger consequences."

The protest was four kilometres from the stadium (another world, in dense urban Sao Paulo), and the metro station near the demonstration closed early in the protest after it filled with tear gas.

"The police are conditioned to act a certain way because they are military: They have to fight the enemy," Mr. Ventura said. "They're acting on a direct order from the government, to protect the big companies that are their allies, and their investments."

In Brazil, most urban policing is done by state military police, a hangover of the dictatorship. All police receive minimal training in the basics of public security. In response to questions from The Globe and Mail, a spokesperson from the Rio de Janeiro state military police said its forces are receiving new training on how to do large-scale crowd control and progressive use of force.

A think tank called the Getúlio Vargas Foundation did an online survey of more than 5,000 police officers across Brazil, and 64 per cent responded that they believed they did not have adequate training to respond to demonstrations. Only 10 per cent said they thought their conduct to date in protests had been appropriate. And 60 per cent said their conduct was determined by government orders.

Prof. Cano noted that police say they are attacked by demonstrators, while protesters counter that they only attack police to try to defend the wounded, and both are partly accurate. Police brutality over the past year has scared away all but a core of more radical demonstrators, he said, which means the propensity for violence aimed at the police is also higher.

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Police have acted harshly for decades in their raids on favelas, conducting gunfights in the middle of civilian neighbourhoods and raiding homes at will – but then their targets were heavily armed drug dealers and organized criminals. "The difference is that the demonstrators in the past year have been primarily middle class," noted Roberto Kant de Lima, an anthropologist working in the law school at the Federal University of Fluminense in Rio, "and now people are paying attention to police brutality, which is suddenly seen as unacceptable."

Prof. Kant is part of a pioneering effort to put police through an online course in public safety, and he hopes to train 5,000 officers in the next five years. It will become a mandatory requirement for promotion. "Citizenship in Brazil is associated only with voting, with political rights, not legal rights or social rights.… Formal equality is a very difficult concept to teach to legal people and especially to the police."

Thais Justen Gomes feels the police still operate as though in the dictatorship era. "Our police are not made for democracy," said Ms. Gomes, a 24-year-old Rio law student who was hit in the head with a ceramic bullet while trying to defend another demonstrator from being arrested for not carrying ID (which is not an offence) at an anti-Cup protest last August. "Our police are there to keep people frightened and silent."

The police and some critics say that they are only violent in retaliation or defence, she said. "But you're starting the debate from the wrong point: as if the police and the protesters had the same strength, the same responsibility. A lot of times the things people do – like burning trash on the ground – is to try to stall the police and to build barriers to defend themselves against the police."th a report from Manuela Andreoni