Cuba made fast progress restoring power to swaths of the Caribbean island nation on Tuesday, both in Havana and outlying provinces, even as emergency and grid workers struggled to reach areas ravaged by Tropical Storm Oscar.

Cuba's power-grid operator said it had restored electricity to parts of Havana on Monday following multiple grid collapses over the past four days, while Tropical Storm Oscar lashed the island's eastern end.

By Monday afternoon, around 89 percent of customers in the capital had power again, however many residents outside Havana remained without electricity, according to the authorities.

Hurricane Oscar left six people dead after hitting Cuba over the weekend during a major power blackout, authorities said Monday, as electricity was restored to most of the capital. Cuba was still bathed in darkness on Sunday when Hurricane Oscar made landfall in the eastern part of the country as a Category 1 storm,