French President Emmanuel Macron said wildfires in the Amazon were an "international crisis" and called on this weekend's G7 summit to address the issue.
It came after Brazil’s President Jair Bolsonaro accused non-governmental organisations of setting forest fires in the Amazon.
Wildfires raging in the Amazon rainforest have hit a record number this year, with 72,843 fires detected so far by Brazil's space research centre INPE, as concerns grow over right-wing Mr Bolsonaro's environmental policies.
On Thursday, Mr Macron tweeted: "Our house is on fire. Literally. The Amazon, the lung of our planet which produces 20 per cent of our oxygen is burning.
"It is an international crisis. Members of the G7, let's talk in two days about this emergency."
Britain's prime minister Boris Johnson echoed Mr Macron's sentiments, calling for international action to protect rainforests globally after the "tragic loss of these precious habitats".
The surge in fires marks an 83 per cent increase over the same period last year, the agency said on Tuesday, and is the highest since records began in 2013.
"Everything indicates" that NGOs were going to the Amazon to "set fire" to the forest, Mr Bolsonaro said in a Facebook Live broadcast on Wednesday morning. When asked if he had evidence to back up his claims, he said he had "no written plan," adding "that's not how it's done."
The former army captain turned politician said the slashing of NGO funding by his government could be a motive.
"Crime exists," he said. "These people are missing the money."
Environmental and climate experts labeled his claims a "smoke screen" to hide his government's dismantling of protections for the world's largest tropical rainforest. They said farmers clearing land were responsible for the uptick in fires.
"This is a sick statement, a pitiful statement," said Marcio Astrini, Greenpeace Brazil's public policy coordinator. "Increased deforestation and burning are the result of his anti-environmental policy."
Politicians in the country also came out against Mr Bolsonaros comments. Former Environment Minister Marina Silva accused Mr Bolsonaro of spreading “fake news and sensationalism” on Twitter Wednesday evening.
“This irresponsible attitude only aggravates the environmental emergency in Brazil,” she wrote.
Congressman Nilto Tatto, leader of the lower house environment caucus, said Mr Bolsonaro's "stunning" attack on NGOs was an attempt to obscure his administration's destruction of 30 years of Brazilian environmental protections.
As the fires worsened this week, celebrities and climate activists shared images of fires ripping through swathes of Amazonian rainforest using the hashtag #PrayForAmazonas as scientists claimed a fifth of the total area of the forest could be lost.
Since last Thursday, INPE said satellite images spotted 9,507 new forest fires in the country, mostly in the Amazon basin.
The Amazon rainforest holds the title the ‘lungs of the world’ for a reason - it’s over 400 million trees and dense vegetation produce a fifth of the globe’s oxygen by absorbing millions of tons of carbon every year. Brazil is home to 60 per cent of the region which is vital to countering global warming.
The knock-on effect of the destruction could turn into a ‘carbon bomb’, scientists have said.
Meanwhile, Brazil’s largest city was plunged into darkness on Monday afternoon as thick dark smoke blotted out the sun. Strong winds blew the smoke 2,700 kilometres from the burning rainforest area to Sao Paulo.
Earlier this month, Norway and Germany suspended funding for projects to curb deforestation in Brazil after becoming alarmed by changes to the way projects were selected under Bolsonaro.