SAO PAULO, BREAZIL -- The number of fires in the Brazilian Amazon last month was the second-highest in a decade for August, nearing the crisis levels that unleashed a flood of international condemnation last year, official figures showed Tuesday.

Fires meanwhile tripled year-on-year in the Pantanal, the world's largest tropical wetlands, according to data based on satellite images from Brazil's national space agency, causing alarm on a new front.

Despite guarantees from President Jair Bolsonaro's government that it is acting to curb the destruction, there were 29,307 fires in the Brazilian Amazon last month, just 5.2 per cent lower than August 2019, according to the space agency, INPE.

It said one of its satellites had experienced technical problems, meaning the real number of fires may have been even higher.

Last year the number of fires in the Brazilian Amazon surged nearly 200 percent year-on-year in August to 30,900, sending a thick haze of black smoke all the way to Sao Paulo, thousands of kilometers away.

That caused worldwide alarm over the devastation to the world's biggest rainforest, a vital resource for curbing climate change.

August often marks the start of fire season in the Amazon, when farmers and ranchers who have felled trees on their land take advantage of dryer weather to set them alight.

Under international pressure, Bolsonaro has deployed the army to the region to crack down on deforestation and fires, and decreed a ban on all agricultural burning.

But environmentalists remain sharply critical of the far-right leader, a climate-change skeptic who has called to open protected Amazon lands to mining and agro-business.

"Last year, images of the Amazon in flames made headlines around the world. This year, the tragedy is repeating itself. Yet the government wants to cut the (environment ministry's) budget next year," Romulo Batista, spokesman for environmental group Greenpeace, said in a statement, accusing Bolsonaro of "dismantling" Brazil's environmental protection agencies.

"The data confirm the failure of the costly and badly planned operation by the Brazilian armed forces in the Amazon, which the Bolsonaro government has tried to substitute for a real plan to fight deforestation," said the Climate Observatory.

Meanwhile, August was the second-worst month on record for fires in the Brazilian Pantanal, with 5,935, behind only August 2005, with 5,993.

Situated at the southern edge of the Amazon and stretching from Brazil into Paraguay and Bolivia, the Pantanal is known as one of the most biodiverse regions on Earth.