About 2,000 Peruvians joined the protest march in the northern city of Cajamarca, carrying signs reading "Let's defend our sources of water, now or never."

Anti-riot police stood guard during the protest, which ended peacefully. In early December, the government had imposed a state of emergency to restore order after a general strike and clashes with police in which dozens of people were injured.

Protesters fear the Conga mine, which would produce gold and copper as well as silver, will taint their water and affect a major aquifer. The mine is majority owned by U.S.-based Newmont Mining Corp.

"I'm sure the population will keep defending its water resources," said Cajamarca state Gov. Gregorio Santos, who has helped lead the protests.

He reiterated that the protesters want a new study of the environmental impact of the mine, and are asking the government to facilitate dialogue about the issue.

Cajamarca is one of Peru's most heavily mined regions and many residents mistrust the new project because it is an extension of nearby Yanacocha mine, Latin America's largest gold mine, which is nearing the end of production. It has a history of troubled relations with neighboring farmers, ranchers and city dwellers downstream who claim it has harmed water supplies.

Newmont spokesman Omar Jabara said a thorough study of environmental impacts has already been performed and reviewed by multiple government agencies. He said the company welcomes "the government's effort to re-review" that assessment.

Jabara said the public has had ample opportunities to raise any issues about the mine in the past. "Some are using Conga today to advance their political agenda," Jabara said in an emailed statement.

Peru's economy depends heavily on mining, which accounts for 61 percent of its export income.