In this photo released by Brazil's indigenous peoples' agency Funai, 'uncontacted' tribesmen react to an overflight by agency officials. Funai warns that illegal logging and mining are putting such communities at risk of disease and cultural annihilation. (Gleison Miranda, Funai/Associated Press)

Officials in Brazil released photographs Friday of what's believed to be one of the last groups of indigenous people in the world that hasn't had face-to-face contact with outsiders.

Brazil's National Indian Foundation, known as Funai, spotted members of the group during flights over the far western Amazon jungle near the Peruvian border.

The people were sighted in an Ethno-Environmental Protected Area along the Envira River in flights over remote Acre state.

Funai said it photographed "strong and healthy" warriors, six huts and a large planted area. But it was not known to which tribe they belonged, officials said.

"Four distinct isolated peoples exist in this region, whom we have accompanied for 20 years," Funai's Jose Carlos Meirelles Junior said in a statement.

Funai does not make contact with the isolated communities of the Amazon area, and it is supposed to prevent invasions of their land, to ensure total autonomy for the remote groups of indigenous people.

The London-based organization Survival International said indigenous tribes in the area are in danger from illegal logging in Peru, which is driving tribes over the border and could lead to conflict with the estimated 500 uncontacted Indians now living on the Brazilian side.

There are more than 100 "uncontacted" tribes worldwide, most of them in Brazil and Peru, the group said in a statement.

"These pictures are further evidence that uncontacted tribes really do exist," Survival International director Stephen Corry said.

"The world needs to wake up to this, and ensure that their territory is protected in accordance with international law. Otherwise, they will soon be made extinct."

With files from the Associated Press