Cuba's national power grid collapsed on Friday. This was reported by "Reuters", citing a statement by the country's network operator UNE.
This is the second complete power outage in a week and the fourth this year.
"A restoration process is underway," the Ministry of Energy said on social media.
The power outages have increased social tensions and led to protests.
US President Donald Trump imposed an oil blockade on the Caribbean island after Washington ousted Venezuelan President Nicolas Maduro on January 3.
Venezuela was the main beneficiary of fuel for Cuba, and subsequent pressure from the US led Mexico to cut off oil supplies to the island.
Havana blames the decade-long US trade embargo for the problems, while Washington attributes the outages to mismanagement of Cuba's state-owned economy.