Brazil's Amazon rainforest has seen a record number of fires this year, new space agency data suggests.
Brazil's National Institute for Space Research (Inpe) said its satellite data showed an 84 percent increase on the same period in 2018, just weeks after President Jair Bolsonaro sacked the head of the agency over its deforestation data.
Mr Bolsonaro has been criticised by conservationists, who said he encouraged loggers and farmers to clear the land, and scientists who said the rainforest has suffered losses at an accelerated rate since he took office in January.
Wildfires often occur in the dry season in Brazil but they are also deliberately started in efforts to illegally deforest land for cattle ranching.
Inpe said it had detected more than 74,000 fires between January and August - the highest number since records began in 2013. It said it had observed more than 9500 forest fires since Thursday, mostly in the Amazon region.
In comparison, there are slightly more than 40,000 in the same period of 2018, it said. However, the worst recent year was 2016, with more than 68,000 fires in that period.
The satellite images showed Brazil's most northern state, Roraima, covered in dark smoke, while neighbouring Amazonas declared an emergency over the fires.
It was earlier reported that a blackout on Monday in the city of São Paulo - more than 2700km away - had been caused by smoke from the Amazon fires.
Some meteorologists say the smoke came from major fires burning in Paraguay, which is much closer to the city and not in the Amazon region.
Meanwhile, US space agency Nasa said that overall fire activity in the Amazon basin was slightly below average this year, with increases in Amazonas and Rondonia, it had decreased in the states of Mato Grosso and Pará.
Mr Bolsonaro brushed off the latest data, saying it was the "season of the queimada", when farmers use fire to clear land.
"I used to be called Captain Chainsaw. Now I am Nero, setting the Amazon aflame," he was quoted by Reuters news agency as saying.
Later he appeared to suggest that non-governmental organisations had set fires, as revenge for his government slashing their funding. He presented no evidence and gave no names to support this theory, saying there were "no written records about the suspicions".
"So, there could be... I'm not affirming it - criminal action by these 'NGOers' to call attention against my person, against the government of Brazil. This is the war that we are facing," he said in a live video stream on Wednesday.
Inpe noted that the number of fires was not in line with those normally reported during the dry season.
"There is nothing abnormal about the climate this year or the rainfall in the Amazon region, which is just a little below average," Inpe researcher Alberto Setzer told Reuters.
"The dry season creates the favourable conditions for the use and spread of fire, but starting a fire is the work of humans, either deliberately or by accident."
Ricardo Mello, head of the World Wide Fund for Nature (WWF) Amazon Programme, said the fires were "a consequence of the increase in deforestation seen in recent figures".
The largest rainforest in the world, the Amazon is a vital carbon store that slows down the pace of global warming. It is also home to about three million species of plants and animals, and one million indigenous people.