Peru's government on Wednesday began a 30-day state of emergency to help it gain control of chronic violence against mining companies, most recently a riot that left three people dead and many wounded.

The object of Tuesday's violence was a massive gold and copper project known as Minas Yanacocha being developed by U.S.-based Newmont Mining Corp. (NYSE:NEM), the world's second-largest gold miner by output, and its partners. Opponents of the project say the venture will pollute their drinking water and otherwise damage regions around the mine.

The state of emergency follows Friday's public warning by Newmont's CEO that the $5 billion project can only advance if there is a "consistent environment that we would need for the successful conduct of both mining and all those things that go with mining, whether that is transporting people or equipment," according to Dow Jones.

Newmont Mining Corp. (NYSE:NEM) shares rose 42 cents to $47.93 in premarket trading.

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