AREQUIPA, PERU, April 22 (Reuters) - Opponents of Southern Copper Corp's proposed $1.4 billion Tia Maria mine in Peru expanded their month-long protests against the project on Wednesday with rallies in several towns in the region.
Demonstrators called on the government to cancel the copper project, stalled since protests turned violent in 2011, over fears it will pollute nearby agricultural valleys.
The protests on Wednesday were scattered throughout Peru's southern region of Arequipa, where Southern Copper hopes to start building Tia Maria this year.
The government approved the project's revised environmental impact study last year and a construction permit is pending.
But renewed demonstrations have threatened to further delay the project, which is expected to add 120,000 tonnes of copper to the company's annual output.
Unions, university students and local political groups marched in the regional capital of Arequipa on Wednesday while farmers rallied in surrounding valleys.
"Yes to agriculture! No to mining!" protesters chanted in the main square of the city Arequipa.
Organizers said the demonstrations were the biggest so far, with tens of thousands turning out across the region.
About 800 marched against Tia Maria midday in downtown Arequipa, according to a Reuters witness.
Clashes between demonstrators and police broke out in the Valley of Tambo where the latest round of protests kicked off a month ago, said Jesus Cornejo, the head of the local farmers' group and a chief opponent.
President Ollanta Humala has defended Tia Maria and urged its detractors to give it a chance.
But talks earlier this week between his government and project opponents, including four local mayors, yielded no agreement.
"The solution is to cancel the project," said Cornejo. "No matter what they say we know it will hurt agriculture."
Southern Copper, controlled by Grupo Mexico, made several revisions to its first environmental impact study to allay those concerns, including agreeing to build a desalinization plant.
The company operates two other mines in the region, Cuajone and Toquepala.
Past mining pollution and poor communication of the technical aspects of Tia Maria have fostered mistrust in local communities, said Manuel Ricardo Amat, the Arequipa head of the country's ombudsman office.
Conflicts over mining projects in Peru, the world's third-biggest copper producer, have held up billions in potential investments in the past decade.
In 2011, Newmont Mining Corp indefinitely suspended its proposed $5 billion gold and copper mine, Conga, after protests by communities turned violent. (Reporting By Mitra Taj; Editing by Cynthia Osterman)