Thousands of opponents of a 5 billion dollars gold project of Newmont Mining circled a lake high in the Andes, in Cajamarca province vowing to stop the company from eventually draining it to make way for Peru's most expensive mine.
Lake Perol is one of several lakes that would eventually be displaced to mine ore from the Conga project. Water from the lakes would be transferred to four reservoirs that the US company and its Peruvian partner, Buenaventura, are building or planning to build.
The companies say the reservoirs would end seasonal shortages and guarantee year-round water supplies to towns and farmers in the area, but many residents fear they would lose control of the water or that the mine would cause pollution.
The 4,000 protesters arrived at Lake Perol on foot or on horseback, many wearing ponchos, as well as traditional broad-brimmed straw hats or baseball caps. Some carried blankets and bags of potatoes and rice, planning to camp out at the site for weeks to halt the project.
Why would we want a reservoir controlled by the company when we already have lakes that naturally provide us water? asked Angel Mendoza, a member of a peasant patrol group from the town of Pampa Verde.
The controversy over Conga - which many in the business sector see as essential for the country's bustling economy - has posed a major challenge to President Ollanta Humala during his nearly two years in office.
He has twice shuffled his cabinet in the face of violent protests against the project.
The protest on Monday was largely peaceful and there were no clashes with police, though a handful of protesters threw rocks and set fire to a wall near one reservoir.
Newmont and Buenaventura said in a statement: As stated previously, we will only build the proposed Perol reservoir if we are able to secure all the necessary permits and complete an intensive public involvement process with neighbouring communities.
We respect everyone's right to safely and responsibly express their opinion, whether they oppose mining or support economic development, the statement said.
In May, a minor clash between protesters and police marked an end to a stretch of nine months of relative calm since August, when Humala's government said it would stop trying to overcome local opposition to the mine.
The new round of protests came after a top official for the Conga project, Chief Executive Roque Benavides of Buenaventura, told Reuters water from Perol would be transferred to a new reservoir later this year. He later said the project might be in jeopardy if water from the lakes could not be transferred.