Rights groups say the decision is a turnaround for Perupetro, which previously had indicated it might open up the protected areas for bidding.

"This decision acknowledges a certain standard ... that there will be no exploration or extraction of natural resources on lands inhabited by un-contacted tribes," said David Hill, a researcher with Survival International, an advocacy group.

He said encroaching oil and gas workers risk exposing tribes that shun contact with outsiders to diseases, and threaten their populations.