Cuba has suffered another nationwide blackout, leaving millions without electricity amid severe fuel shortages and US restrictions on oil supplies. It is at least the sixth major outage the island has experienced since the start of the year.

Under a US embargo for decades, Cuba has faced worsening fuel shortages since Venezuela, previously Havana’s main oil supplier, stopped shipments following the US capture of President Nicolas Maduro in January.

US President Donald Trump subsequently declared a national emergency over Cuba, moving to block oil shipments to the island and threatening tariffs against countries that continued supplying it. Trump has repeatedly said he intends to take Cuba “one way or another,” and described regime change there as a “question of time.”

Cuba’s Ministry of Energy and Mines said the latest grid collapse was triggered on Friday by a transmission-line failure in the western part of the country and compounded by unstable weather.

Officials immediately activated restoration protocols, gradually bringing generating facilities back online. Power had returned to parts of the island by Saturday.

Cuba’s electricity system relies heavily on aging oil-fired power plants, many of which have operated for decades and require frequent maintenance. Fuel shortages and difficulties obtaining spare parts have forced generating units offline, leaving the grid with little spare capacity when other facilities fail.

Washington has meanwhile stepped up economic pressure on Havana. On Thursday, US Secretary of State Marco Rubio announced new sanctions targeting Cuba’s nickel sector, following measures imposed on state oil company CUPET in June.

Russia, China, Mexico, and several other countries have provided humanitarian assistance to Cuba. Russia delivered around 700,000 barrels of oil in late March, one of the few major fuel shipments to reach the island since US restrictions were tightened.

The worsening shortages have disrupted electricity, transportation, water supplies, and healthcare. In June, UN High Commissioner for Human Rights Volker Turk warned that “children [in Cuba] are dying because doctors lack access to essential medical supplies and medicines.”

“Such severe sanctions packages that target entire sectors of an economy and produce broad, indiscriminate and harsh effects on populations are incompatible with basic principles of international human rights law,” he said.