Swathes of Amazon forest have been stripped of vegetation in apparent preparation for burning.

Blackened tree trunks lay smoldering on the charred ground as thick smoke chokes the Amazon rainforest in Brazil, a scene of devastation that is being repeated across the "lungs of the planet."

In the northwestern state of Rondonia -- one of the hardest hit areas by the worst fires in years -- people are living under a blanket of smoke that has enveloped the remote region.

"I've lived here for 20 years and I've seen a lot of fires, but this smoke in recent days, I've never seen anything like that before," Welis da Claiana, 25, told AFP in the capital Porto Velho.

"The smoke has affected 100 percent of our daily lives. We wake up tired from breathing the smoke."

Da Claiana says the fires in recent days had even threatened the car hire company where she works and forced the cancellation of flights at the local airport.

"Visibility was horrible, no one could do anything," she said, blaming "big farmers" for the blazes.

At one point, the fires began closing in on her home. She shut the doors and windows in an attempt to keep out the smoke, but she still ended up having to rush her daughter to the hospital after she began having difficulty breathing.

A colleague was also hospitalized with respiratory problems.

The cause of the air pollution can be found a short drive from the city of half a million people: multiple fires devouring sections of forest that have been cleared to make way for cattle or crops.

Seen from above, the destruction is dramatic: walls of bright orange flames advance across the expansive forest as huge plumes of black smoke billow into the sky.

Swathes of forest have been stripped of vegetation in apparent preparation for burning. AFP journalists traveling by road and air in the state bordering Bolivia have seen others on fire or already burned to a crisp.

In some places, a single tree has been left standing, surrounded by scorched earth -- a testament to the destruction of a forest the WWF says is home to hundreds of threatened animal and plant species.

More than half of the 79,513 fires recorded in Brazil this year are in the Amazon, and 1,130 were started between Friday and Saturday.

"It's increasing every year," Eliana Amorim said in Porto Velho, blaming deforestation for the fires.

"But people's awareness is not."