Peru declared a 30-day state of emergency in the Apurimac region on Tuesday after four people were killed during anti-mining protests.
The four were shot dead in clashes between police and protesters at the Chinese-owned Las Bambas mine project.
Locals fear the $7.4bn (£4.9bn) copper mine project will cause environmental damage to the Andean area.
The government said extra troops would be sent to Apurimac “to restore internal peace”.
Curbs on liberties
While the state of emergency is in force, police are able to search homes without a warrant and freedom of assembly is suspended.
It is the second time this year a state of emergency has been declared in Peru to quell anti-mining protests.
In May, a state of emergency was declared for 60 days in the province of Islay in Arequipa after protests against the Tia Maria copper mine turned deadly.
The protests in Apurimac began on Friday.
They escalated on Monday when some of the estimated 2,000 demonstrators tried to move onto land owned by the mining project near the town of Challhuahuacho.
Fourteen protesters and eight police officers were injured.
Locals are angry about changes to the project’s environmental impact plan, which they say they were not consulted about.
They say that under the new plan, the area and its groundwater are at risk from contamination.
Peru is currently the third biggest producer of copper after Chile and China.
It is seeking to overtake China but its ambitions have been hampered by local opposition to the projects.