HAVANA, Cuba —  A power outage struck the entire island of Cuba on Saturday, the energy ministry said, in the second nationwide blackout in less than a week as its grid struggles under a US oil blockade. Buildings began to lose power in Havana before nightfall, shortly before 6:30 pm (2230 GMT) and just five days after the previous one plunged the country into darkness. A "total disconnection" of the national electricity system took place, the energy ministry said in a post on X, adding that work had begun to restore power. The blackout occurred as an international aid convoy began to arrive in Havana this week, bringing sorely-needed medical supplies, food, water and solar panels to the island. Cuba's ageing electricity generation system is in shambles, with daily power outages of up to 20 hours the norm in parts of the island, which lacks the fuel needed to generate power. But since the January 3 US ouster of Cuba's top ally, Nicolas Maduro of Venezuela, the island's economy has been hammered further as President Donald Trump maintains a de facto oil blockade. No oil has been imported to the island since January 9, hitting the power sector while also forcing airlines to curtail flights to the island, a blow to the all-important tourism sector. The crisis in the country of 9.6 million people comes as Trump has made no secret of his desire to see regime change in Havana. The blackouts as well as regular shortages of food, medicine and other basics are spurring frustrations, with demonstrators vandalizing a provincial office of the Cuban Communist Party last weekend.