LIMA, May 12 (Reuters) - Protesters upset over oil and natural gas developments in the resource-rich Amazon are threatening to choke energy supplies in northern Peru, the country's environmental minister said on Tuesday.

Peru's government is encouraging investment in hopes of turning the country into a net oil exporter from a net importer.

But some communities in the central regions of Loreto, Amazonas, Ucayali and Cuzco have been demonstrating for weeks, demanding the government revoke decrees aligning Peru's laws with a recently signed free-trade pact with the United States.

Protesters fear the new rules make it easier for foreign companies to control land, especially in the Amazon rain forest.

"In some regions, a state of emergency has been declared because they were blocking oil pumping stations 5 and 6," Environmental Minister Antonio Brack told reporters, referring to installations of state-run energy company Petroperu.

A Petroperu official declined to comment when asked whether the pumping stations were working.

Similar protests last year forced the company to stop using its northern pipeline for more than a week. The pipeline pumps some 27,000 barrels of oil a day.

Peru's government, which has auctioned off mining and energy concessions throughout most of the country, has drawn fierce criticism from environmental and human rights groups. They say development threatens to damage the environment and risks exposing remote tribes to new and deadly diseases.

The country signed 13 oil and natural gas contracts this year and has said it will auction off at least another dozen sites in July.

Resources found below ground in Peru belong to the national government, not to local communities.

"In this, the government will not make changes," said Brack. "We cannot compromise the country's energy security."

Calls to Petroperu's office in Piura, where its refinery is located, were not immediately returned. (Reporting by Dana Ford; Editing by Hilary Burke; Editing by David Gregorio)

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