In 2019, the number of fires in Brazil's rainforests increased by 83 percent, compared to the corresponding period last year, according to satellite images. On Monday, the country's largest city, São Paulo, was covered in black smoke for several hours - a result of the massive fires currently raging in the country, according to international media.

Satellite images show the country's northernmost state, Roraima, covered in black smoke and in the nearby Amazon have been declared emergency, the BBC writes.

The US space research authority Nasa says that while seeing an increase in fires in the Amazon and in Rondônia - fires in states such as Mato Grosoo and Pará are decreasing, the BBC writes.

Over 72,000 fires

The forest fires usually occur during Brazil's dry periods, but also start by illegal deforestation.

From January to August, Inpe has mapped over 72,000 fires - which is the highest figure since 2003. This is about 40,000 more fires than during the corresponding period 2018.

Jair Bolsonaro critical

The country's president, Jair Bolsonaro, dismisses the information. He has previously been accused of encouraging deforestation - and scientists believe the Amazon has fallen sharply to the surface since taking office, the BBC writes.

However, Brazil's space research authority, the National Institute for Space Research (Inpe), believes that the number of fires does not match what is normally reported during the season.

"There is nothing abnormal about the climate this year or the rainfall in the Amazon, which is just below average," Alberto Setzer, a researcher at Inpe told Reuters news agency.