A British mining company is facing a multi-million pound claim for damages after group of protesters were detained and allegedly tortured at an open cast copper mine that the firm is seeking to develop in the mountains of northern Peru.

In a case that will highlight growing tensions between powerful mining interests in Peru and alliances of poor subsistence farmers and environmentalists, the high court in London is to hear harrowing accounts of people held for three days at the remote mine near the border with Ecuador.

When the protesters marched to the mine they found armed police waiting for them. They say the police were being directed by the mine’s managers — although its owner, Monterrico Metals, disputes this. After firing teargas at the protesters, the police detained 28 people and bound their hands behind their backs.

The detainees say noxious substances were sprayed in their faces before they were hooded, beaten with sticks and whipped. Two of the protesters were women who say they were sexually assaulted and threatened with rape.

A further three protesters were shot and wounded by police, and while there is no suggestion the mining company was responsible for this, the protesters claim one of those shot was left to bleed to death at the mine site. A postmortem examination found that he took about 36 hours to die.

Although Monterrico says it had no control over the police operation, lawyers for the protesters have taken statements from eyewitnesses alleging that the mine’s manager was directing the police, and say that two of the corporation’s executives had been in the area shortly before and during the police operation.

A Peruvian journalist who was detained along with the protesters has since been handed a series of photographs of the police operation, allegedly taken by a Monterrico supervisor, which the protesters say support their allegations of abuse by the police.

Several of the photographs were taken outside the mine’s offices and show the bloodied protesters with their hands bound, while others show groups of blindfolded or hooded protesters herded together on the company’s property. A number of the photographs show grinning police officers waving the female protesters’ underwear.

One picture shows a farmer called Melanio Garcia, 41, lying on the ground, apparently alive but badly injured. Several other pictures, taken 30 hours later according to their time and date stamps, clearly show Garcia to be dead. The company says he was shot some distance from the mine.

On Friday Richard Meeran, a solicitor with Leigh Day, the London law firm bringing the high court case, obtained a freezing injunction which obliges the company to keep at least £5m of its assets in the UK.

Monterrico says a police officer was shot in the leg by the protesters, and that the demonstrators were detained because of this assault.

A spokesman said: “Monterrico vigorously denies that any of its officers or employees were in any way involved with the alleged abuses at the Rio Blanco mine in 2005 and that it considers allegations to the contrary made by the claimants to be wholly without merit.”