Cuba's power-grid operator said it had restored electricity to most of the capital Havana on Monday even as Tropical Storm Oscar lashed the island's eastern end, downing trees and power lines.

Cuba's power grid has ground to a halt for a second time in as many days, leaving 10 million on the island without power and the Caribbean island in a growing sense of crisis.

Tropical Storm Oscar doused Cuba on Monday, three days after a massive power failure plunged more than 10 million people into the dark as the island worked to restore its decades-old power grid.