Brazil's Amazonian forest fires are reported to have reached indigenous tribal reserves, raising fears that loggers and land usurpers are targeting these remote areas during a surge in fires that swept the world's largest rainforest.

The fire was seen in the Araripoia reserve in Maranahao state, a tree that was heavily razed on the eastern edges of the Amazon, home to about 80 people from an isolated group of indigenous Awa, whom the non-governmental organization Survival International has described as the world's most endangered tribe.

Deliberate fires are often used to clear pastures and desertified areas of the Amazon during the dry winter months, but there have been 2,800 fires this month more than any August since 2010.

Home of the Oro Io Wow Wow tore swept away ( Reuters )

The paper said Brazilian President Jair Bolsonaro had been accused of helping fuel the crisis by encouraging invasion campaigns to the reserves with his promises to develop the Amazon and impose his vision of progress on indigenous peoples.

Activists say indigenous lands are easy targets for loggers, farmers and settlers looking for valuable land or timber. One said research based on NASA photos revealed that fires had broken out in 131 reserves from August 15 to 20.

Of these, 15 protected areas were home to indigenous communities isolated or in early contact with the outside world.

On the other side of the Amazon, fires broke out in and around the Oro Io Wau Wau Reserve in Rondonia, home to three indigenous groups, in voluntary isolation, raising activists' concerns because they do not know what will happen to these groups.