Environment Minister Ricardo Salles says the fires have spread to "gigantic proportions". Nevertheless, President Jair Bolsonaro said on Wednesday that the criticism levelled against his government over the fires in the Pantanal and also in the Amazon region had been "disproportionate".
A jaguar crosses a river near Porto Jofre, Mato Grosso state - EPA
The basin, which thrives off annual flooding following torrential rains, is home to jaguars, piranhas, capuchin monkeys, green anacondas and thousands of plant species.
A number of jaguars fleeing the fires are moving towards one corner of the Encontro das Aguas State Park - EPA
Forest fires often occur naturally in the dry season in Brazil but they are also deliberately started by ranchers trying to clear land for cattle.
A drone image shows a burnt out building in the middle of the forest - Shutterstock
Experts say it is impossible to calculate yet how many animals have been killed by the fires, but losses are feared to be huge.
A caiman killed by fire - EPA
Smoke fills the air in the Pantanal - EPA
A veterinarian helps a coati with fire burns on its legs in Pocone, Mato Grosso state - EPA
A burnt-out turtle shell - EPA
Veterinarians feed a deer affected by the blazes - EPA