Brazilian troops backed by military aircraft on Saturday prepared to deploy in the to fight fires that have swept the region and prompted anti-government protests as well as an international outcry.
Some 44,000 troops will be available for "unprecedented" operations to put out the fires, and forces are heading to four Brazilian states that asked for federal help to contain the blazes, defence minister Fernando Azevedo said.
The states are Roraima, Rondonia, Tocantins and Para.
The military's first mission will be the deployment of 700 troops to the area around Porto Velho, capital of Rondonia, Mr Azevedo said.
He added that the military will use two C-130 Hercules aircraft capable of dumping up to 12,000 litres (3,170 gallons) of water on fires.
An Associated Press journalist flying over the Porto Velho region Saturday morning reported hazy conditions and low visibility.
On Friday, the reporter saw many already deforested areas that were burned, apparently by people clearing farmland, as well as a large column of smoke billowing from one fire.
The Brazilian military operations came after widespread criticism of president Jair Bolsonaro's handling of the crisis.
On Friday, the president authorised the armed forces to get involved in putting out the fires, saying he is committed to protecting the Amazon region .
"It shows the concern of Bolsonaro's government about this issue," Mr Azevedo said. "It was a very fast response."
Mr Bolsonaro has previously described rainforest protections as an obstacle to Brazil's economic development, sparring with critics who say the Amazon absorbs vast amounts of greenhouse gasses and is crucial for efforts to contain climate change.
The Amazon fires have become a global issue, escalating tensions between Brazil and European countries who believe Mr Bolsonaro has neglected commitments to protect biodiversity.
Protesters gathered outside Brazilian diplomatic missions in European and Latin American cities Friday, and demonstrators also marched in Brazil.
The dispute spilled into the economic arena when French leader Emmanuel Macron threatened to block a European Union trade deal with Brazil and several other South American countries.
He wants G7 leaders meeting at a summit in France this weekend to discuss the Amazon crisis.
"First we need to help Brazil and other countries put out these fires," Mr Macron said Saturday.
The goal is to "preserve this forest that we all need because it is a treasure of our biodiversity and our climate thanks to the oxygen that it emits and thanks to the carbon it absorbs", he said.
Bolivia and Paraguay have also struggled to contain fires that swept through woods and fields, in many cases set to clear land for farming.
A US-based aircraft, the B747-400 SuperTanker, is flying over devastated areas in Bolivia to help put out the fires and protect forests.
Fires are common in Brazil in the annual dry season, but they are much more widespread this year.
Brazilian state experts reported nearly 77,000 wildfires across the country so far this year, up 85% over the same period in 2018.
