Amid growing international criticism over the wildfires raging through the Amazon, Brazilian President Jair Bolsonaro on Thursday admitted farmers could be illegally setting the rainforest ablaze but told foreign powers not to interfere.

The threat to what some call "the lungs of the planet" has ignited a bitter dispute about who is to blame.

Bolsonaro traded Twitter jabs on Thursday with France's president over the fires.

French President Emmanuel Macron called the wildfires an international crisis and said the leaders of the Group of 7 nations should hold urgent discussions about them at their summit in France this weekend.

"Our house is burning. Literally. The Amazon rain forest — the lungs which produces 20% of our planet's oxygen — is on fire," Macron tweeted.

Bolsonaro fired back with his own tweet: "I regret that Macron seeks to make personal political gains in an internal matter for Brazil and other Amazonian countries. The sensationalist tone he used does nothing to solve the problem."

On Wednesday, Bolsonaro blamed non-governmental organizations for setting the fires, without providing evidence. He appeared to row back on Thursday, when he said for the first time that farmers could be behind the fires.

They may have had at least tacit encouragement from the firebrand right-wing president, who took power in January. Bolsonaro has repeatedly said he believes Brazil should open the Amazon up to business interests, to allow mining, agricultural and logging companies to exploit its natural resources.

Onyx Lorenzoni, the president's chief of staff, earlier in the day accused European countries of exaggerating environmental problems in Brazil in order to disrupt its commercial interests.

"There is deforestation in Brazil, yes, but not at the rate and level that they say," said Lorenzoni, according to the Brazilian news website globo.com.

His allegation came after Germany and Norway, citing Brazil's apparent lack of commitment to fighting deforestation, decided to withhold more than $60 million in funds earmarked for sustainability projects in Brazilian forests.

On Friday Irish Prime Minister Leo Varadkar was quoted as saying Ireland will try to block a free trade deal between the European Union and South America unless Brazil takes action to protect the rainforest.

Brazil contains about 60 percent of the Amazon rainforest, whose degradation could have severe consequences for global climate and rainfall.