Subways in Brazil's largest cities, Rio and Sao Paulo, still face problems in functions as the FIFA World Cup is approaching.

On Monday, in Sao Paulo, three of the five subway lines confronted mechanical problems, causing trains to be evacuated and taken to maintenance, and commuters long delays in reaching their workplaces.

And in Rio, smoke invaded a subway train at a station and made passengers panic. Though the subway company denied that there was fire, passengers told daily O Globo that there was, indeed, a fire and subway workers used fire extinguishers at the platform.

The incidents are only the latest in a series of accidents and malfunctions in the subway systems of Rio and Sao Paulo, both of which will host matches of the FIFA World Cup starting in June.

The opening match of the World Cup will be held in Sao Paulo and the final in Rio.

The poor quality and high fare prices of public transportation in Brazil were the fuse for the protests which shook over Brazil in June 2013.

The protests started in Sao Paulo after the authorities announced a fare rise, and spread to Rio, where public transit price also increased, and to several other cities.

The 2016 Summer Olympics will also take place in Rio.