By Nick Butler

Protesters close to the stadium in Sao Paulo where the first match of the FIFA World Cup will take place next month ©AFP/Getty ImagesProtests have taken place throughout Brazil today as embers of the violence which rocked the country during the Confederations Cup last summer reignite with less than a month to go until the opening of the FIFA World Cup. 

Although the unrest has socio-economic overtones as well as a political dimension, with five months to go until the Presidential elections, the costs associated with hosting the World Cup appears the foremost cause for the unrest. 

In business hub São Paulo, around 5,000 members of the Homeless Workers' Movement set fire to car tyres and marched towards the Corinthians Arena, due to host the opening match between Brazil and Croatia on June 12.

In response riot police fired tear gas to disperse the protesters. 

More than 200 metalworkers also held a protest against unemployment outside a factory in the south of the city, while there were reports of several other demonstrations elsewhere, as well as roads being blocked and cars being set on fire. 

Protests have also taken place in Rio de Janeiro, where the World Cup final is scheduled to be played at the Maracanã Stadium on July 13, while there have been calls for protests via social media in at least 10 of the 12 cities hosting matches. 

The most serious clashes have been in the northern city of Recife, where an undisclosed number of Federal troops have entered the city today after shops and supermarkets were ransacked overnight.

This comes after state police went on strike on Tuesday (May 13) demanding higher salaries, with schools and universities closed due to concerns for student safety.

Although this is seemingly less connected to the World Cup than eruptions elsewhere, Recife is set to host five matches during the tournament, starting with a clash between Ivory Coast and Japan on June 14.

As with during the Confederations Cup last year, the World Cup is providing a focal point for wider discontent ©AFP/Getty ImagesAs with during the Confederations Cup last year, the World Cup is providing a focal point for wider discontent ©AFP/Getty Images

Although at this stage there are a far smaller number of protesters involved than during the Confederations Cup last summer, when there were several deaths after days of disruption throughout the country, the increasingly radical and organised nature must be a concern.

An anonymous group also hacked the official website of Sao Paulo's World Cup Organising Committee yesterday and put up the slogan: "Without rights there will be no World Cup".

Today's events will be a particular blow after the Brazilian Government optimistically forecast yesterday that World Cup tourist spending in Brazil in June and July may exceed $3 billion (£1.8 billion/€2.2 billion).

Brazil has spent more than $11 billion (£7 billion/€8 billion) to organise the month-long event, money protesters say could have been better spent on pressing needs in areas such as transport, education and health care.

But the Government has played down the significance of the unrest, with Sports Minister Aldo Rebelo insisting, from his perspective, "these are specific claims by workers".

"I've seen nothing that is related to the [World] Cup," he added.

"There's no reason to panic ahead of receiving three million Brazilian tourists and 600,000 foreign tourists."