"Strong winds caused by the major hurricane Rafael caused the shutdown of the national electricity system," the Union Electrica company wrote on X.

Rafael strengthened to a major Category 3 hurricane as it raced towards the Caribbean island, where it was expected to make landfall in the next few hours, according to the National Hurricane Center in the United States.

The NHC said in an update at 2100 GMT that Rafael was located 75 kilometers (about 45 miles) southwest of Havana, expected to bring "a life-threatening storm surge, damaging hurricane-force winds and destructive waves."

Wednesday's blackout comes two weeks after a four-day nationwide electricity outage caused by the failure of the island's biggest power plant and a shortage of fuel to produce electricity.

That initial blackout coincided with the passage of Hurricane Oscar, which killed eight people in Cuba.

More than 70,000 people have been evacuated from their homes in advance of Rafael's approach, according to local media.