A LARGE power outage left millions of people across Chile in darkness on Tuesday.

The blackout affected the South American nation from the northern Arica and Parinacota region to the southern Los Lagos area.

The country’s grid operator said a disruption had occurred in a high-voltage transmission line that carries power from the Atacama Desert to the capital of Santiago.

The National Electrical Coordinator did not say what actually caused the disruption that pushed much of Chile’s power grid into shutdown.

Authorities in Santiago, a city of some 8.4 million people, said there would be no subway service until further notice.

Interior Minister Carolina Toh said hospitals, prisons and government buildings were switching on backup generators to keep essential equipment operating.

In a press conference, Toh urged the public to stay calm and said officials were racing to put the grid back in operation and restore electric service across the country of some 19 million people.

“It’s affecting the entire electrical system of the country,” she said of the breakdown in the 500-kV backbone transmission line.

Toh said if all areas didn’t return to normal by sunset the government would take emergency measures to avert a crisis.

One of the country’s main electricity distributors, Saesa, confirmed that all of its customers had experienced the power failure.

Officials said they were evacuating passengers from darkened tunnels and subway stations in Santiago and elsewhere in the country, including the coastal tourist hotspot of Valparaiso.

Videos on social media from all over Chile showed chaos at intersections with no functioning traffic lights.

People also had use their mobile phones as torches in the underground metro and police were dispatched to help evacuate office buildings.

Transport Minister Juan Carlos Muoz urged people to stay home.

At the very most, he said just 27 per cent of city traffic lights are working.

Mobile phone services also blinkered offline in parts of the country.

Authorities at Santiago International Airport said terminals had switched to emergency power to keep flights operating as usual.