The collapse follows nationwide blackouts last year that plunged Cuba's frail power-generating system into disarray.

Cuba blames the mounting crisis on a Cold War-era U.S. trade embargo and fresh restrictions from U.S. President Donald Trump, who recently tightened sanctions on the communist-run government and vowed to restore a "tough" policy toward the long-time U.S. foe.

The grid failed on Friday evening about 8:15pm (00:15 GMT) after a breakdown at Diezmero substation in the capital, Havana, kicked off a chain reaction that shut down power generation across the island, according to officials at operator Union Electrica (UNE).