Brazilian President Jair Bolsonaro has accused Hollywood star Leonardo DiCaprio of financing fires being set in the Amazon rainforest, without presenting any evidence.

Key points: Jair Bolsonaro has long claimed that environmental groups are setting fires in the Amazon

Jair Bolsonaro has long claimed that environmental groups are setting fires in the Amazon Police have accused four members of a local fire brigade of deliberately setting fires to drum up donations

Police have accused four members of a local fire brigade of deliberately setting fires to drum up donations WWF denies obtaining photos from the firefighters or receiving a donation from DiCaprio

Mr Bolsonaro appeared to be commenting on social media postings claiming the World Wildlife Fund (WWF) had paid for images taken by volunteer firefighters that it then supposedly used to solicit donations, including an alleged $US500,000 contribution from DiCaprio.

"This Leonardo DiCaprio is a cool guy, right? Giving money to torch the Amazon," Mr Bolsonaro said on Friday during brief remarks in front of the presidential residence.

The comment came on the back of a live-streamed webcast on Thursday when Mr Bolsonaro first attacked DiCaprio.

The President said the WWF paid the firefighting NGO to take pictures of forest fires in the Amazon.

Smoke billows during a fire in an area of the Amazon rainforest near Porto Velho in Brazil. ( Reuters: Bruno Kelly )

"So what did the NGO do? What is the easiest thing? Set fire to the forest. Take pictures, make a video," the President said.

"(WWF) makes a campaign against Brazil, it contacts Leonardo DiCaprio, he donates $500,000."

"A part of that went to the people that were setting fires. Leonardo DiCaprio, you are contributing to the fire in the Amazon, that won't do."

The WWF has denied receiving a donation from DiCaprio or obtaining photos from the firefighters.

DiCaprio has denied donating to the WWF.

In a statement, the actor lauded "the people of Brazil working to save their natural and cultural heritage".

But, he added, "while worthy of support, we did not fund the organisations targeted".

DiCaprio has been an outspoken advocate on behalf of combating climate change, speaking frequently about environmental issues including the Amazon forest fires.

Four members of the non-governmental organisation Alter do Cho Fire Brigade were arrested on Tuesday, with police accusing them of deliberately setting fires in order to document them and drum up more donations.

Brazil's President Jair Bolsonaro accused WWF and Leonardo DiCaprio of setting fire in the Amazon. ( Reuters: Ueslei Marcelino )

They were released on Thursday on a judge's order.

Politicians and other NGOs fiercely criticised the arrest, saying it was part of a concerted attempt by Mr Bolsonaro's government to harass environmental groups.

Intentional fires and deforestation in the Amazon reached levels not seen in a decade earlier this year.

Scientists and activists blame land speculators, farmers and ranchers for setting the fires to clear land for agricultural use, saying that deforesters are being emboldened by Mr Bolsonaro's rhetoric of promoting development and farming over preservation.

Some members of Mr Bolsonaro's administration argue that civil society groups and environmental laws hinder economic development in the region.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 2 minutes 2 m Wildfires in Brazil have destroyed vast swathes of the Amazon rainforest.

Mr Bolsonaro has repeatedly lashed out at various factions in casting blame for the forest fires.

In a Facebook live post on August 21, he said "everything indicated" that NGOs were going to the Amazon to "set fire" to the forest.

When asked then if he had evidence to back up his claims, Mr Bolsonaro said he had "no written plan," adding, "that's not how it's done."

One day later he admitted that farmers could be illegally setting the rainforest ablaze, but roughly a month later he attacked the "lying media" for saying that the rainforest was being devastated by the fires.

ABC/wires