WATCH this eerie footage of a huge river that mysteriously turned blood red.

The waters of the Rimac River running through Lima, the capital of Peru, took on the unsettling hue – but officials insisted it was still safe to drink.

Locals and officials were alarmed by the ominous change to the river, which is the country’s most important water source.

The video shows onlookers staring down in horror from bridges at the discoloured water rushing beneath them on Tuesday.

The entire river – tens of metres wide – had blushed bright red.

The phenomenon was filmed between the Trujillo Bridge and the Chabuca Granda avenue in the centre of Lima.

Witnesses had no explanation for the striking sight and took to social media to share their surprise.

One wrote: “I just passed the yellow line and the Rímac River is red at this point!”

Another said: “This is how the Rímac River is red,” alongside footage of the scene.

Maria Angelica Villasante, an environmental expert, explained that the colour change was not the work of a “curse”, as some speculation suggested.

Rather, she believes it is a result of coloured pollutants flowing into the water from industrial plants in the area.

There are at least 30 operating mines in the surrounding Santa Eulalia basin and more than 500 drainage pipes that flow directly into the river.

Maria believes discharges from these mines are what dyed the water crimson.

The local water supplier, Sedapal, acknowledged the strange colour change, but insisted that the water was still safe to drink.

The company said that “the collection and treatment of water in our plants is continues as normal, strictly complying with quality standards”.

Addressing the colouration, it said: “The change in the colour of the water occurs downstream of our intake gates , so it does not represent a risk for the supply process.”

It reaffirmed its commitment to supplying “quality drinking water to the population, ensuring a safe and reliable service”.

The National Water Authority said it had visited the river and taken samples.

It promised: “We will continue to fulfil our supervisory role by measuring the quality of water from natural sources to deliver the results to the competent authorities, and if any alteration is found, the corresponding actions will be taken as soon as possible.”

The Rimac River is 160km-long and divides the northern and southern regions of the capital.

A similar alarming sight confused Aussies in December.

Sydney locals discovered blood red seawater foaming around a wooden pier in the city – baffling even the experts.