Tuesday's announcement by the Ministry of Defense says that 7,500 troops have been sent to patrol the area in an operation that is expected to last two weeks.
Defense Minister Celso Amorin says that the neighboring countries were invited to send observers.
This is the sixth such operation this year. Three more are expected in 2013.
The operations are meant to combat a range of crimes, including trafficking in animals, drugs, arms and illegally harvested wood.
These military actions also take medical and dental care to remote populations.
(Copyright 2012 The Associated Press. All rights reserved.)