At least one million people rallied across Brazil on Thursday in escalating mass demonstrations over the quality of public services and the high cost of staging the World Cup, police and experts said.

The mounting pressure on the government of President Dilma Rousseff in the face of the biggest street protests the South American country has seen in 20 years prompted her to cancel a trip to Japan planned for next week.

Security forces struggled to maintain order in several cities, firing tear gas and rubber bullets to disperse groups of rowdy protesters who hurled stones and lit fires.

Police fired tear gas in Rio de Janeiro, scene of the biggest protest where 300,000 people demonstrated near City Hall, while in the capital Brasilia, security forces blocked protesters trying to break into the foreign ministry and throwing burning objects.

Police and experts, quoted by Brazilian media, said at least one million marched in more than 100 cities across the country of 194 million people, an intensification of a movement sparked two weeks ago by public anger about a hike in public transport fares.

The protests have spiraled into a wider call for an end to government corruption in the world's seventh largest economy, a call fueled by resentment over the $15 billion cost of hosting the Confederations Cup and the World Cup.

In Rio, police fired tear gas to disperse a small group of stone-throwing protesters. At least one person was hurt in the clashes, which sparked panic in the crowd.

Demonstrators also set ablaze a vehicle owned by the SBT television station.

A protester died after a motorist hit him and two other demonstrators in the southeastern city of Ribeirao Preto, police said.

In the northeastern city of Salvador, one of the host cities for the Confederations Cup, police fired tear gas against some of the 20,000 protesters massed two kilometers (1.2 miles) from the stadium where Uruguay defeated Nigeria 2-1.

Vehicles used by world football's governing body FIFA were stoned in the Bahia state capital and riot police had to intervene.

The Inter-American Commission on Human Rights, meanwhile, called for an investigation into the possible use of "excessive force" on demonstrators and journalists during protests last week.

On Wednesday, protesters had scored a major victory when authorities in Rio and Sao Paulo, Brazil's two biggest cities, canceled the controversial transit fare hikes, but that was not enough to placate the demonstrators.

In Sao Paulo, an estimated 110,000 people flooded the main Paulista Avenue to celebrate the fare rollback and keep the pressure on Rousseff's leftist government to increase social spending.

"Victory, this is just the beginning," one huge banner read.

"Miracles happen when people unite," another read, while several protesters called for Rousseff, Sao Paulo State Governor Geraldo Alckmin and Sao Paulo Mayor Fernando Haddad to be impeached.

The protest was largely peaceful except for clashes between a group of ultra-leftists marching behind their red banners and a majority of demonstrators who objected to the presence of political parties.

"This is a social movement, not a political movement. This has nothing to do with ideology," 28-year-old protester Maria Vidal told AFP. "We don't want parties in the demonstration."

One of the leftists was hit in the head by a projectile and blamed a member of Rousseff's ruling Workers Party. Police were forced to intervene to end the melee.

Protesters say they want higher funding for education, health and housing. They are also railing against what they view as rampant corruption within the political class.

In Belo Horizonte, 15,000 people, most of them in their 20s, gathered just before dusk on the Alfonso Pena thoroughfare, but a prompt police response of rubber bullets sent them scuttling for cover.

"Brazil, country of corruption," "We want a serious economic policy," "Enough, it's time to speak" and "Brazil is waking up," were just some of the slogans marchers held aloft as they wound their way through the city center.

"I know that in principle staging the Cup is good for Brazil. This should bring development and money. But for decades, the governments we have had have just wasted money," explained Thiago, a 28-year-old medical student.

Clashes between demonstrators and police were also reported in Recife and Vitoria.

As the protests heated up in the evening, Rousseff's office announced that she would not travel to Japan on June 26-28 as planned for talks with Prime Minister Shinzo Abe.

"She has decided to stay in Brazil due to current events," a source in her office said.

Social media networks have been key to the organization of the mass protests, with demonstrators using the slogan "It's more than just 20 cents" -- a reference to the bus fare hikes -- to rally people to their cause.

The movement has no political coloration and no clearly identified leadership.

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