Cuba on Friday experienced a nationwide blackout after the island's main power plant failed, causing the country's electricity grid to collapse, the energy ministry said.

"The system was left without power nationwide" after the unexpected shutdown of the Antonio Guiteras power plant, Lazaro Guerra, director general of electricity at the ministry of energy and mines, told state television.

When the thermoelectric plant shut down "the system collapsed," he said, adding the government was working to restore service as soon as possible.

On Thursday, Prime Minister Manuel Marrero announced the island was in the throes of an "energy emergency," with severe supply shortages leaving some provinces without power for up to 20 hours.

The government on Thursday suspended all non-essential public sector activities in order to prioritize electricity supply to homes.

Cuba gets its power from eight ageing thermal power plants, as well as seven floating plants leased from Turkish companies.

The island nation has been under a severe embargo by the United States since 1958. (AFP)