More than 30 people, many of them police officers, have been injured in clashes in southern Peru.
Violence broke out in the city of Arequipa, during a protest against plans for copper mining.
Farmers fear Southern Copper Corp’s Tia Maria project will contaminate their land and crops.
Police fired tear gas in an effort to disperse the crowds, while protesters hurled rocks at riot police.
Tia Maria has faced delays since 2011, when rallies by farmers left three dead. Three people have also been killed in renewed protests this year, just ahead of construction.