The Brazilian government says it took the images to prove the tribe exists and help protect its land.
The pictures, taken from an aeroplane, show red-painted tribe members brandishing bows and arrows.
More than half the world's 100 uncontacted tribes live in Brazil or Peru, Survival International says.
Stephen Corry, the director of the group - which supports tribal people around the world - said such tribes would "soon be made extinct" if their land was not protected.
'Monumental crime'
Survival International said that although this particular group is increasing in number, others in the area are at risk from illegal logging.
The photos were taken during several flights over one of the most remote parts of the Amazon rainforest in Brazil's Acre region.
They show tribe members outside thatched huts, surrounded by the dense jungle, pointing bows and arrows up at the camera.
"We did the overflight to show their houses, to show they are there, to show they exist," the group quoted Jose Carlos dos Reis Meirelles Junior, an official in the Brazilian government's Indian affairs department, as saying.
"This is very important because there are some who doubt their existence."
He described the threats to such tribes and their land as "a monumental crime against the natural world" and "further testimony to the complete irrationality with which we, the 'civilised' ones, treat the world".
Disease is also a risk, as members of tribal groups that have been contacted in the past have died of illnesses that they have no defence against, ranging from chicken pox to the common cold.
http://news.bbc.co.uk/2/hi/americas/7426794.stm
http://news.yahoo.com/s/ap/20080530/ap_ ... il_indians
http://www.google.com/search?hl=en&q=Un ... tnG=Search
someone explain please. 
