Hurricane Irma has pounded Cuba's northern coast and is now barrelling towards Florida as authorities scramble to complete an unprecedented evacuation of millions of residents before the storm engulfs the US state.
The outer band of Irma, which has killed at least 22 people in the Caribbean, was already lashing South Florida with tropical storm-force winds and left nearly 25,000 people without power, Governor Rick Scott said.
The brunt of the hurricane, one of the fiercest Atlantic storms in a century, is due to arrive in Florida early on Sunday.
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Irma could inflict major damage on the fourth-largest US state by population, which is braced for winds well in excess of 160km/h and a huge storm surge that could trigger coastal flooding.
"This is a deadly storm and our state has never seen anything like it," Mr Scott said at a Saturday morning news conference.
Irma, located about 365km south of Miami on Saturday morning, still ranked as a Category 5 storm when it crashed into Cuba in the early hours of Saturday. It weakened to a Category 3 as it tore along the island's northern coastline, downing power lines, bending palm trees and sending huge waves crashing over sea walls.
Maximum sustained winds dipped to around 215km/h by 8am local time on Saturday, the US National Hurricane Center said.
But Irma will regain strength as it moves over the warm open water as it approaches Florida, according to the NHC, which expects the storm to arrive in the Keys, an archipelago off the peninsula's southern tip, on Sunday morning.
On Florida's West Coast, a long line of people in Estero, north of Naples, lined up to enter an arena that officials converted into an evacuation shelter, one of hundreds that have opened up across the state.
The destruction along Cuba's north central coast was similar to that seen on other Caribbean islands over the last week as Irma plowed into Ciego de Avila province around midnight.
State media said it was the first time the eye of a Category 5 storm had made landfall since 1932. In the days before Irma struck, the island's government evacuated tens of thousands of foreign tourists from resorts on the northern coast.
In Ciego de Avila province, Irma was forecast to generate waves of up to 7 metres, with flooding expected as far west as the capital Havana, authorities said on Saturday.
With the storm barrelling toward the United States, officials in Florida raced to overcome clogged highways, gasoline shortages and move elderly residents to safety.
A total of 5.6 million people, or 25 percent of the state's population, were ordered to evacuate Florida, according to the Florida Division of Emergency Management.