Deforestation in Brazil's Amazon increased by 15 percent during the past 12 months, the National Institute for Space Research (INPE) said.
From July 2010 to July 2011 the vast South American rainforest lost 2,654 square kilometers (1,649 square miles) of vegetation in the states of Mato Grosso and Para, according to a preliminary analysis of satellite photos.
The year before, 2,295 square kilometers (1,426 square miles) were destroyed over that time period.
This July, 225 square kilometers (139 square miles) were lost to deforestation, though this was significantly less than the 485 square kilometers (301 square miles) destroyed in July 2010.
In April 477 square kilometers (296 square miles) were destroyed, with more than 95 percent of the devastation taking place in Mato Grosso, which is a major agricultural frontier used for cattle ranches and soybean farming.
Wednesday's figures were calculated from a satellite system known as DETER, which detects in real time when an area larger than 61 acres is destroyed, though its results are not always exact due to cloud cover.
Brazil, the world's fifth largest country by area, has 5.3 million square kilometers of jungle and forests -- mostly in the Amazon river basin -- of which only 1.7 million are under state protection.
The rest is in private hands, or its ownership is undefined.
Deforestation has made Brazil one of the world's top greenhouse gas emitters, and the pace of deforestation peaked in 2004 at 27,000 square kilometers (10,000 square miles) a year.
The rate of deforestation has declined since then, in part because of DETER, and at the 2009 UN climate change summit in Copenhagen, Brazil committed itself to reducing Amazon deforestation by 80 percent by 2020.
Explore further: Switzerland 1st country to submit pledge for UN climate pact