HAVANA (AP) — Cuba's national energy grid suffered a major failure early Thursday that severed power to the island's eastern provinces, authorities said, as residents in the capital Havana faced ongoing blackouts.

Cuba's aging power grid has eroded in recent years as it faces a prolonged economic crisis, recently made worse by a U.S. energy blockade of the island, where daily life can be an ordeal for many of the country's 10 million people.

The state-run Electric Union said the collapse had stripped power from all eastern provinces from Guantánamo to Ciego de Ávila, and that crews were working to restore power, but it did not give an estimate for how long it would take.

The previous day, Cuban President Miguel Díaz-Canel had described the energy situation as "tense" after supplies of oil delivered by a Russian vessel in late March ran out. Cuba produces barely 40% of the fuel it needs to power its economy.

Russia announced plans to send a second fuel ship to Cuba in early April. According to Russian news reports, the oil tanker left the Russian Baltic port of Vysotsk in January, but has been stuck in the same place in the Atlantic Ocean for the last several weeks.