Brasilia: Darkness reportedly descended on Sau Paolo, Brazil in the middle of the afternoon as the Amazon rainforest continued to burn, causing social media users to say that it looked “apocalyptic”.

Wildfires raging in the Amazon rainforest have hit a record number this year, with 72,843 fires detected so far by Brazil's space research centre (INPE), as concerns grow over right-wing President Jair Bolsonaro's environmental policy.

The surge marks an 83% increase over the same period of 2018, the agency said on Tuesday, and is the highest since records began in 2013. On Thursday, INPE said satellite images spotted 9,507 new forest fires in the country, mostly in the Amazon basin, home to the world's largest tropical forest seen as vital to countering global warming.

Images show the northernmost state of Roraima covered in dark smoke. Amazonas declared an emergency in the south of the state and in its capital Manaus on Aug. 9. Acre, on the border with Peru, has been on environmental alert since Friday due to the fires.

Wildfires have increased in Mato Grosso and Para, two states where Brazil's agricultural frontier has pushed into the Amazon basin and spurred deforestation. Wildfires are common in the dry season but are also deliberately set by farmers illegally deforesting land for cattle ranching.