Deforestation of Brazil's Amazon has slowed for a fourth consecutive year to its lowest rate since authorities began monitoring the world's largest rainforest, officials said Tuesday.

The National Institute of Space Research found that the Amazon lost 4,656 square kilometers (1,797 square miles) of rain forest over a period running from August 2011 to July 2012, 27 percent less than the previous year.

"It is the lowest deforestation rate since Brazil began its monitoring" in 1988, said Environment Minister Izabella Teixeira.

"I believe that it is the only good piece of environmental news," she told a press conference called to unveil a new electronic system to slap fines on those found guilty of deforesting the Amazon.

A year ago, INPE reported that the Amazon lost 6,238 square kilometers (2,408 square miles) of rainforest between August 2010 and July 2011, 11 percent less than the previous year.

Declines in the extent of deforestation have been registered in each of the past four years.

Destruction of forests releases large quantities of CO2, which account for 17 percent of the greenhouse gas emissions that cause global warming.

Large-scale deforestation has made Brazil one of the world's top greenhouse gas emitters, but the government has made significant strides in curbing it over the past decade.

Key causes of Amazon deforestation are fires, the spread of agriculture and stockbreeding and illegal trafficking in timber and minerals.