Aerial footage shows plumes of smoke in the Amazon

According to government data, the first 12 days of August have seen about the same number of fires as this time last year, when a sharp increase in blazes across the Amazon attracted international condemnation.

On Tuesday (August 11), Brazil's President Jair Bolsonaro denied there were any fires in the Amazon, calling it a "lie" and blaming the media for spreading it.

Experts say that fires are rarely a natural phenomenon in the rainforest, resulting instead from deliberate burning by farmers and land speculators to clear deforested land for pasture.

Wind and heat can quickly change the pattern of a blaze. Even rainfall from months ago can make a difference.

Deforestation rose 34.5% in the 12 months through July, compared to a year earlier.

Bolsonaro has dispatched the military to fight fires and deforestation since May, but environmental experts question whether these deployments are working.