As Britain pledged over $12 million in help, Brazil deployed two C-130 Hercules aircraft to douse fires devouring parts of the Amazon rainforest. Hundreds of new blazes flared up and thousands protested over the destruction.
Heavy smoke covered the city of Porto Velho in the northwestern state of Rondonia where the defence ministry said the planes have started dumping thousands of litres of water, amid a global uproar over the worst fires in years.
Swathes of the remote region bordering Bolivia have been scorched by the blazes, sending thick smoke billowing into the sky and increasing air pollution across the world's largest rainforest, which is seen as crucial to mitigating climate change.
Experts say increased land clearing during the months-long dry season to make way for crops or grazing has aggravated the problem this year.
"In a week where we have all watched, horrified, as the Amazon rainforest burns before our eyes, we cannot escape the reality of the damage we are inflicting on the natural world," British Prime Minister Boris Johnson said in a statement on Monday.
Johnson pledged $12.3 million would be made available immediately to help restore the habitat, including areas that have been hit by the fires, the statement, released at the G7 summit in the French resort of Biarritz, said.
The pledge came after French President Emmanuel Macron, who is hosting the summit, said Sunday that world leaders had agreed to help the countries affected by the wildfires as soon as possible.
Although about 60 percent of the Amazon is in Brazil, the vast forest also takes in parts Bolivia, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname and Venezuela.
Macron's bid to put the Amazon crisis high on the agenda at the G7 angered Brazil's far-right leader Jair Bolsonaro, who lashed out over what he sees as outside interference, denouncing the French leader's "colonialist mentality".
Worse each year
"It gets worse every year – this year, the smoke has been really serious," Deliana Amorim, 46, said in Porto Velho, where half a million people live.
Seven states, including Rondonia, have requested the army's help in the Amazon, where more than 43,000 troops are based and available to combat fires, officials said.
Dozens of firefighters went to Porto Velho on Sunday to help put out the blazes.
Justice Minister Sergio Moro has also given the green light for the deployment of security forces to tackle illegal deforestation in the region.
TRT World's Reagan Des Vignes reports.
EU-Americas trade deal at risk
The fires threaten to torpedo a huge trade agreement between the European Union and South American countries, including Brazil, that took 20 years to negotiate.
EU Council President Donald Tusk told reporters at the G7 on Saturday that it was hard to imagine European countries ratifying a trade pact with the Mercosur bloc as long as Brazil fails to curb the fires ravaging the Amazon.
Pope Francis on Sunday also voiced concern for the rainforest, which he described as a "vital" lung for the planet.
Under intensifying pressure, Bolsonaro on Friday vowed a "zero tolerance" approach to criminal activities in the Amazon and promised strong action to control the fires.
Days earlier, he had accused non-government organisations of igniting the blazes after their funding was cut.
"There are forest fires all over the world, and this cannot be used as a pretext for possible international sanctions," Bolsonaro said, after issuing a decree authorising the deployment of armed forces.
Bolsonaro told reporters Saturday the fires were affecting areas already cleared, not the remaining forest.
TRT World speaks to Rhett Butler, the founder and CEO of Mongabay.
'Bolsonaro leave, Amazon stay'
The latest official figures show 79,513 forest fires have been recorded in Brazil this year, the highest number of any year since 2013.
More than half of the fires are in the massive Amazon basin, where more than 20 million people live. Some 1,130 new fires were ignited between Friday and Saturday, according to Brazil's National Institute for Space Research (INPE).
Thousands of protesters took to the streets in the fashionable Ipanema neighbourhood of Rio de Janeiro on Sunday, after demonstrations across the country and in Europe on Friday.
Chanting "Bolsonaro leave, Amazon stay", protesters demanded the government do more to protect the forest.
"The nature is being destroyed," Teresa Correa, from the northern state of Para, said.
"The situation is worse since he (Bolsonaro) became –– he wants to explore and destroy everything."