Irma's rampage across northern Cuban took the lives of 10 people, officials said Monday as the scope of the disaster came more fully into view.
President Raul Castro said Cubans face "hard days" with homes built with effort torn down in just a few hours by the storm, which struck the island late Friday as a top intensity Category Five hurricane.
"It is not time to mourn, but to rebuild what the winds of Hurricane Irma have tried to wipe out," Castro said in comments published in the official newspaper Granma.
Cuba's civil defense organization reported that 10 people were killed, with causes of death including electrocution, building collapse and a balcony falling onto a bus.
Castro said Irma had caused "severe damage to the country" but he added that the scale of the destruction had yet to be fully established because of its country's size.
Havana was hammered by winds up to 150 kilometers (93 miles) per hour, with an unprecedented storm surge swamping parts of the capital and leaving many people waist-deep in water.
Some of the victims had ignored instructions to evacuate, the civil defense authority said.
Seven of the deaths occurred in the capital.
A fourth floor balcony in a dilapidated neighborhood of Havana collapsed on a passing bus, killing two women inside.
A 71-year-old man was electrocuted by a downed power line while trying to move his TV antenna, and another man of 77 was crushed by a falling electricity pole.
In the center if the city, two men were killed when the roof of a house collapsed and the body of an 89-year-old woman was found floating in water inside her house, near Havana's iconic seaside Malecon esplanade.
The other victims died in the western province of Matanzas, Ciego Avila in the center and Camaguey in the east as the storm "seriously" damaged the center of the island with winds up to 256 kilometers (159 miles) per hour, according to Cuban state media.
Authorities said they evacuated more than a million people overall as a precaution.
The hurricane killed at least 25 people earlier on its path across the Caribbean.
Irma weakened early Monday to a tropical storm as it continued on a northward path through Florida..