A Brazilian research institute says the area deforested in the country's Amazon region in the one-year period through July increased an estimated 22 percent from the previous year.
The National Institute for Space Research announced on Thursday that during the period, the Amazon in Brazil lost 13,235 square kilometers of rainforest. That's the most since 2006.
The Amazon is the world's biggest tropical rainforest. About two-thirds of it lies in Brazil.
Brazilian Environment Minister Joaquim Leite vowed to take quick action, stressing the need to step up measures against illegal logging in the forest.
At the UN COP26 climate change conference in Britain, Brazil's government disclosed its new target of ending illegal logging by 2028.
But the latest figure shows deforestation has accelerated under the administration of President Jair Bolsonaro, who supports developing the Amazon.
A local environmental group says government officials hid the deforestation data before the UN conference.