"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.

Perupetro had been under pressure for months to limit exploration activities near tribal areas, and had cast doubt on the existence of isolated indigenous groups, angering activists.

But this week it changed its tune and on Thursday it confirmed none of the 17 hydrocarbon lots it started auctioning this week will overlap with protected national parks.

"We are obligated to comply with the law and with certain restrictions that limit the economic activity on these lands," said Winston Wusen, a Perupetro executive.