Hurricane Oscar's arrival to eastern Cuba Sunday has impacted millions of residents already facing days without power, as fresh attempts to restore much of the nation's electric grid have failed.

Cuba has had four electric grid collapses since Friday, and most of the country remains in the dark as slow progress is made to restore power.

Cuba's efforts to restore power to the island were derailed for a third time late on Saturday, Cuban authorities said shortly before midnight, leaving millions in the dark and raising fresh questions over the viability of the government's bid to reestablish electrical service.