Hurricane Dorian, is causing devastation in the Bahamas as winds measuring up to 220mph slam the Caribbean.
Footage posted on social media shows homes lying in ruin in the Bahamas' Abaco Islands, with flood water running through the streets.
The Category 5 hurricane, which is the second most powerful Atlantic hurricane on record, is expected to move through the islands before heading towards Florida and up the east coast of America.
Hazards for the Abaco Islands included storm surges 18 to 23 feet (5.5 to 7metres) above normal tide levels with higher destructive waves, the Miami-based US National Hurricane Center (NHC) said.
State governors in South Carolina and Georgia have ordered the evacuations of their coasts in anticipation of the hurricane making landfall in the US.
It is estimated up to 1.5million people could be ordered to flee.
The NHC said Dorian slammed into Elbow Cay in the Abaco Islands with maximum sustained winds of 185mph and gusts of more than 220mph.
The Royal Navy has deployed an aid ship, RFA Mounts Bay, to potentially help stricken residents in the Bahamas, CNN reports.
The vessel, which was last seen around the British Virgin Islands, is capable of conducting rescue missions as it is carrying a range of amphibious vehicles and a helicopter.
The hurricane is less than 150 miles away from the Florida coast, with parts of the state being evacuated.
Georgia's governor Brian Kemp has ordered a mandatory evacuation of the state's coast starting at noon on Monday ahead of Hurricane Dorian.
South Carolina governor Henry McMaster also told people to leave the state's shoreline earlier today, with all of the schools and government offices in the area to shut on Tuesday morning.
The mandatory evacuation of cities and counties along the coast will start at noon (local time).
The state has reversed lanes on roads heading towards the coast, enabling greater numbers to flee to safety.
Mr McMaster said medical evacuations have already begun, according to The State .
Millions of people from Florida to North Carolina are bracing for Dorian's possible landfall or for the storm to veer north into the Atlantic Ocean.
The hurricane is expected to near Florida's east coast on Monday, before moving northwards towards Georgia and South Carolina.
Dorian is forecast to remain a hurricane for the next five days, the NHC said.
In Florida, at least seven counties issued mandatory evacuations for some residents, including those in mobile homes, on barrier islands and in low-lying areas.
Palm Beach County, the third most-populated county and home to President Donald Trump's Mar-a-Lago resort, was among those with partial mandatory evacuations.
Other counties announced voluntary evacuations.
