At least three people have been killed and 20 injured during clashes between security forces and demonstrators protesting a planned $4.8 billion gold mine by US-based Newmont in northern Peru.
A 17-year-old was among those dead, and 15 people were also arrested at the Conga mining project, Cajamarca region prosecutor Esperanza Leon told RPP radio.
More than 1,000 protesters threw stones at government offices in the town of Celendin, and police responded by firing tear gas and using their batons to disperse the crowd, local media reported.
During the scuffle, two police officers were wounded by "guns fired by protesters who were trying to take over Celendin," the interior ministry said in a statement. It accused the demonstrators of committing "criminal acts."
The Peruvian government declared a state of emergency in Cajamarca, suspending freedom of assembly, the inviolability of the home and freedom of movement. It also mobilized the military to support police operations.
Protesters say the Conga mining project will pollute the area's lakes and rivers, contaminating water supplies.
The demonstration came after Celendin Mayor Mauro Arteaga was said to have expressed support for the project.
Conga was approved in 2010 by former president Alan Garcia's government. His successor President Ollanta Humala had been a backer of the project but insists potential environmental impacts must be weighed.
The open-pit project, located some 3,700 meters (12,140 feet) above sea level, involves moving the water from four lagoons high in the Andes mountains into reservoirs the company would build.
Construction is due to begin in 2014.