Peruvian authorities say they are struggling to keep outsiders away from a clan of previously isolated Amazon Indians who began appearing on the banks of a jungle river popular with environmental tourists last year.
The behavior of the small group of Mashco-Piro Indians has puzzled scientists, who say it may be related to the encroachment of loggers and low-flying aircraft from nearby natural gas and oil exploration in southeast Peru.
Clan members have been blamed for two bow-and-arrow attacks on people near the riverbank in Madre de Dios state where officials say the Indians were first seen last May.
One arrow badly wounded a forest ranger in October. The following month, another fatally pierced the heart of a local Matsiguenka Indian, Nicolas "Shaco" Flores, who had long maintained a relationship with the Mashco-Piro.
The advocacy group Survival International released photos Tuesday showing clan members on the riverbank, describing the pictures as the "most detailed sightings of uncontacted Indians ever recorded on camera."
The British-based group provided the photos exactly a year after releasing aerial photos from Brazil of another tribe classified as uncontacted, one of about 100 such groups it says exist around the world.
The Mashco-Piro tribe is believed to number in the hundreds and lives in the Manu National Park that borders Diamante, a community of more than 200 people where Flores lived.
Although it's not known what provoked the Mashco-Piro clan to leave the relative safety of the tribe's jungle home, Beatriz Huerta, an anthropologist who works with Peru's agency for indigenous affairs, speculated their habitat is becoming increasingly less isolated.
The upper Madre de Dios region where the tribe lives has been affected by logging, she said. "They are removing wood very close," she said.
Meanwhile, Huerta said, naturalists in the area and Manu National Park officials told her during a recent visit that a rise in air traffic related to natural gas and oil exploration in the region is adversely affecting native hunting grounds, forcing increasing migration by nomadic tribes.
The clan that showed up at the river is believed to number about 60, including some 25 adults, said Carlos Soria, a professor at Lima's Catholic University who ran Peru's park protection agency last year.