Millions in Cuba have been left without power after the national electric grid collapsed on Monday, the country's power operator says.

This is the latest in a series of widespread power outages to hit the country, whose chronic fuel shortages have been exacerbated by a recent US blockade on oil shipments to the island.

UNE, Cuba's grid operator, said it was gradually restoring electricity in provinces and cities around the country.

Cuba, an island of around 10 million people, has battled widespread blackouts in recent years - a persistent source of public discontent that has triggered rare protests.

Cuba relies heavily on imported fuel, and Venezuela was believed to have sent around 35,000 barrels of oil a day to Cuba - accounting for about half of the island's oil needs.

But these shipments have been halted since the US captured Venezuelan president Nicolas Maduro in January.

Since then, the US has ramped up pressure on Cuba by seizing a number of oil shipments bound for the island. US president Donald Trump has also threatened tariffs on any country that supplies oil to Cuba.

No oil shipments have arrived in Cuba in the last three months, according to Cuban president Miguel Diaz-Canel.

Trump told reporters at the White House on Monday that he believed he would have the "honour of taking Cuba".

"Whether I free it, take it, I could do anything I want with it, you want to know the truth. They're a very weakened nation right now."

He previously threatened a "friendly takeover" of Cuba, a long-time foe of the US since communist leader Fidel Castro overthrew a US-backed government in 1959.

Last week, President Diaz-Canel confirmed his government was in the initial stages of talks with the Trump administration to resolve differences.

Widespread power outages - caused by the fuel shortages and faults in its power grid - have triggered protests among Cubans in recent years.

Last week, a Communist Party building in the city of Moron was stormed by protesters after a rally over steep food prices and persistent power cuts.

A Havana resident told Reuters the recent power blackout "didn't surprise" her. "We're getting used to living like this," she said. (BBC)