The release of new photographs of an indigenous group living in extreme isolation in the Amazon rain forest has stirred fresh controversy and new concerns over the fate of the region's so-called uncontacted tribes.

Taken last week from a low-flying aircraft in the far western Brazilian state of Acre (AH-cray), the images depict frightened tribal warriors brandishing spears and arrows as they peer up from palm-thatched huts in the middle of the jungle.

Brazil's indigenous affairs agency, FUNAI, has confirmed the presence of 27 indigenous groups living in extreme isolation in Brazil's vast Amazon region, making it the home of the largest number of uncontacted tribes in the world. (It's possible Brazilian forests may shelter as many as 84 such