Brazil's President Jair Bolsonaro said Friday he is considering deploying the army to help combat fires raging in the Amazon rainforest, as a growing global outcry over the blazes threatens to torpedo a huge trade deal.

The fires in the world's largest rainforest have sparked protests around the planet and ignited a war of words between Bolsonaro and his French counterpart Emmanuel Macron, who has described the wildfires as an "international crisis" and vowed to block a trade agreement between the European Union and South American countries.

The latest official figures show 76 720 forest fires were recorded in Brazil so far this year - the highest number for any year since 2013. More than half are in the Amazon.

Around 700 new fires were ignited between Wednesday and Thursday, according to the National Institute for Space Research (INPE), fueling air contamination in cities including Sao Paulo, where thick smog turned day into night on Monday.

"The tendency is that," Bolsonaro told reporters in Brazil's capital Brasilia when asked if he was considering sending the army to fight the fires.

A decision would be made Friday, he added, after holding a late-night crisis meeting with members of his cabinet.

Bolsonaro's remarks come as demonstrations are held around the world over the fires in the Amazon forest, a region considered the "lungs of the planet" and seen as crucial to keeping climate change in check.

Protests are planned in Brazil's major cities later Friday.

In an escalating public row over the blazes, Macron on Friday accused Bolsonaro of lying to him on Brazil's stance on climate change.

France will now block a trade deal between the European Union and the South American trade bloc Mercosur, which includes Brazil, a French presidential official said.

Macron had tweeted Thursday that fires burning in the Amazon amount to an international crisis and should be discussed as a top priority when the G7 countries meet this weekend in France.

Bolsonaro then blasted Macron for having a "colonialist mentality".

Ireland also threatened to block the trade deal if Brazil failed to curb the fires, Prime Minister Leo Varadkar said Friday.

"The extent of the fires in the Amazon area is shocking and threatening and not only for Brazil and the other affected countries, but also for the whole world," German Chancellor Angela Merkel's spokesman said Friday.

UN chief Antonio Guterres said Thursday he was "deeply concerned" by the fires.

'International pariah'

Environmental specialists say the fires have accompanied a rapid rate of deforestation in the Amazon region, which in July quadrupled compared to the same month in 2018, according to INPE data.

Bolsonaro instead attributes the blazes to increased drought, and accuses environmental groups and NGOs of whipping up an "environmental psychosis" to harm Brazil's economic interests.

Earlier in the week Bolsonaro accused non-government organisations of starting the fires.

Thomaz Favaro of Control Risks consultancy told AFP Bolsonaro's comments were "raising the risks of sanctions and retaliation, including against the EU-Mercosur deal".

"Brazil has gone from being a global model of forest conservation to an international pariah," Robert Muggah, research director at the Igarape Institute, a think tank in Rio de Janeiro, told AFP.

"The president has only himself to blame."

Peru, which contains much of the Amazon basin, announced it was "on alert" for wildfires spreading from neighboring Brazil and Bolivia.

Paraguay and Bolivia are battling separate wildfires that have devastated large areas of their rainforests.

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