Jose Carlos Meirelles, an official from the Brazilian government's Indian affairs department, says the group's numbers are increasing but they are in severe danger from illegal logging in Peru.
"What is happening in this region is a monumental crime against the natural world, the tribes, the fauna and is further testimony to the complete irrationality with which we, the 'civilized' ones, treat the world," Meirelles stated in a statement issued by the Survival International group, which supports tribal peoples around the world.
One of the pictures shows two tribesmen covered in bright red pigment poised to fire arrows at the expedition's aircraft while another tribesman looks on.
Another photo shows about 15 Indians near thatched huts, some of them also preparing to fire arrows at the aircraft.
Stephen Corry, the director of Survival International, 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," he said.
There are more than 100 uncontacted tribes worldwide. More than half live in either Brazil or Peru, Survival International says.
It says all are in grave danger of being forced off their land, killed and ravaged by new diseases.