Peru has declared a state of emergency in jungle areas where indigenous groups are blocking oil and gas installations in protest at a new land sale law.
The government said violent acts by protesters had put security at risk.
The measure allows the authorities to send in troops and bans public gatherings for 30 days.
Some 65 Amazon tribes say the law will make it easier for big energy companies to buy up their land, parts of which are known to be rich in oil and gas.
The indigenous people have been demonstrating for more than a week at hydro-electric dams and oil and gas installations in three different parts of Peru's Amazon basin.
They are angry at a law which they say makes it easier for investors to buy their land because it lowers the bar for consent from two-thirds of a community assembly to a simple majority.
The legislation is one of a number of laws being passed as part of Peru's free trade agreement with the US.
"They have mobilised themselves for the right to life, the right to keep their territory and to defend the environment - the Amazon rainforest which is the lungs of the world," said Alberto Pizango, head of the indigenous Amazonian organisation, AIDESEP.
Indigenous communities complain that some 70% of Peruvian Amazon territory is now leased for oil and gas exploration, putting at risk their own lives and the biodiversity of the Amazon.
At the weekend, some 800 demonstrators and police clashed in the province of Bagua, leaving several people injured.
Talks between the tribes' representatives and the Environment Minister Antonio Brack also fell through.
Mr Brack said there could be no further dialogue until order was re-established.
"The state has the obligation to guarantee the right of all Peruvians when others violate them so order has to be established - let us be absolutely clear on this," Mr Brack said.
The state of emergency bans public gatherings for 30 days and gives the army special powers in the provinces of Cusco, Loreto and Amazonas.
For their part, the tribal groups are calling on the Peruvian Congress to revoke the land law, saying their protests will end once the government displayed a readiness to talk.
The Peruvian rainforest is the biggest stretch of Amazon outside Brazil.
Peruvian President Alan Garcia has said that developing parts of the Amazon are part of his investment programme to tackle widespread poverty.