The country's national grid crashed around midday Friday after the Antonio Guiteras power plant, the island's largest, shut down, causing the biggest blackout in at least two years.

Despite the best efforts of authorities, the grid collapsed again on Saturday morning.

Even in a country stricken by a deepening economic crisis, Friday's collapse was massive and notable and comes as Hurricane Oscar is set to make landfall on Sunday night.

Late on Saturday, efforts to restore power to the island were derailed for a third time, raising questions over the government's bid to re-establish power.

This came after some initial progress had been reported.

"Tonight at 10.25pm the total disconnection of the national electro-energetic system occurred again," the Havana Electric company said on Telegram late on Saturday.

The post was later removed from the company's Telegram feed.

It was not immediately clear why the post was removed, but millions were still without power on early on Sunday.

Shortly after the Havana Electric company's post, Cuba's state agency responsible for energy said: "The process of restoring the electrical system remains complex.

"At around 10.15pm another disconnection of the western subsystem occurred.

"Work continues on its recovery."

The western subsystem includes the capital Havana.

Two small protests took place overnight, one in Marianao and the other in the Cuatro Caminos area of Havana.

Later on Sunday, incremental progress had been made as some neighbourhoods in the Cuban capital had power restored.

Cuba's state agency responsible for energy also said in an update that power had returned to some areas.

But impacts went beyond leaving much of the country in the dark as services like water supply also required electricity to run pumps.

People resorted to cooking on improvised wooden stoves in the streets before food went bad in refrigerators.

After the initial collapse on Friday, the government closed schools and "non-essential" industrial sites to preserve supplies.

Officials did not immediately offer details about what caused the blackout.

Rolling power cuts have plagued the country in recent weeks - as long as 10 to 20 hours a day across much of the island.

Cuban Prime Minister Manuel Marrero said on Thursday the issues had been caused by a combination of infrastructure problems, fuel shortages and rising demand, including from household air conditioning units.

"The fuel shortage is the biggest factor," he said in a televised address.

A US trade embargo, along with sanctions introduced by former president Donald Trump, has also been blamed for reducing supplies of fuel and spare parts needed to repair machinery in Cuba's power plants.

But the White House has hit back at the claims.

A US national security council spokesperson said: "The United States is not to blame for today's [Friday's] blackout on the island or the overall energy situation in Cuba."

Cuba's largest oil supplier, Venezuela, has added to the problems by reducing shipments to the island this year as it grapples with its shortages.

Russia and Mexico have also significantly reduced supplies to the Caribbean country.

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On Saturday, Cuba issued a hurricane warning for its northern coast ahead of Hurricane Oscar's expected landfall on Sunday night, where it could cause a potentially deadly storm surge.

The storm is set to bring winds of up to 85mph, the National Hurricane Center said, along with heavy rainfall that could cause flash flooding and potential mudslides across parts of eastern Cuba.