Rescuers have begun to reach areas of the northern Bahamas devastated by Hurricane Dorian, with aerial images showing a trail of destruction.
PM Hubert Minnis said some areas had been “decimated” and expected the current death toll of seven would rise.
The hurricane winds that hit the Abaco Islands equalled the highest ever recorded at landfall, and Grand Bahama also suffered severe damage and floods.
Dorian has moved off north but still threatens the eastern US seaboard.
Forecasters have warned it could make landfall on the coast of South or North Carolina on Thursday.
Although the hurricane has weakened to a category two storm with maximum sustained winds of 105mph (165km/h), it has grown larger in area.
Mr Minnis confirmed the death toll had risen from five to seven, but added: “We can expect more deaths to be recorded. This is just preliminary information.”
He said the Bahamas was facing “one of the greatest national crises in our country’s history”.
Lia Head-Rigby, who runs a relief group and overflew the Abacos, said her representatives had told her there were “a lot more dead”.
“It’s total devastation. It’s decimated. Apocalyptic,” she told the Associated Press (AP) news agency.
Aerial images over the Abacos, including the port town of Marsh Harbour, showed mile upon mile of destruction, with roofs torn off, scattered debris, overturned cars, shipping containers and boats, and high water levels.
“There’s nothing left in most of Marsh Harbour,” said Alicia Cook, who evacuated from the area. “People are starting to panic: pillaging, looting… it’s just no way everyone’s going to get out.”
Opposition leader Philip Brave Davis described the scenes from a flight over the islands as a “horrible sight”.
Parts of the Bahamas received up to 35in (89cm) of rain.
See extent of flooding in Abaco Islands caused by Hurricane Dorian
The situation on Grand Bahama is less clear, as Dorian only moved on late on Tuesday after nearly two days of pummelling, cutting many communication lines.
Most rescue work was being done on an ad hoc basis by locals using boats and jet skis, but it was being hampered by flooded roads, fallen trees and submerged debris.
Rescue teams were “beginning to get on the ground”, National Security Minister Marvin Dames said on Wednesday, according to AP.
One survivor in Freeport on Grand Bahama, crab fisherman Howard Armstrong, told CNN floodwaters had reached the roof of his house and his wife “got hypothermia and she was standing on top of the kitchen cabinets until they disintegrated… I kept with her and she just drowned on me”.
Mr Minnis said: “Our priority at this time is search, rescue and recovery. It will take all of us as a caring community – government, church, businesses and individuals – to help restore the lives of our people.”
People have taken to social media to post lists of those they have lost contact with during the storm.
The International Red Cross fears 45% of homes on Grand Bahama and the Abacos – some 13,000 properties – have been severely damaged or destroyed.
Some 60,000 people will need food aid and clean water, UN officials say.
A map from the Finnish satellite company ICEYE showed the extent of the flooding on Grand Bahama:
At 18:00 GMT, the National Hurricane Center said Dorian was located about 115 miles (185km) east of Jacksonville in Florida and about 180 miles south of Charleston, South Carolina.
The storm – moving at 9mph (15km/h) – would travel parallel to the Florida and Georgia coasts through Wednesday night, then “near or over” the coasts of the Carolinas through Thursday and Friday, it said.
The NHC warned there was a danger of life-threatening storm surges for coastal communities north of Port Canaveral in Florida all the way to the North Carolina-Virginia border.
Dorian is expected to weaken over the next few days but will remain a powerful hurricane.
President Donald Trump tweeted that the US “may be getting a little bit lucky with respect to Hurricane Dorian, but please don’t let down your guard”.
Scientists cannot say whether climate change is increasing the number of hurricanes, but the ones that do happen are likely to be more powerful and more destructive because of our warming climate, says BBC Weather’s Tomasz Schafernaker.
Use our guide to see how these deadly storms form, their devastating effects and how they are measured:
A guide to the world’s deadliest storms
Hurricanes are violent storms that can bring devastation to coastal areas, threatening lives, homes and businesses.
Hurricanes develop from thunderstorms, fuelled by warm, moist air as they cross sub-tropical waters.
Warm air rises into the storm.
Air swirls in to fill the low pressure in the storm, sucking air in and upwards, reinforcing the low pressure.
The storm rotates due to the spin of the earth and energy from the warm ocean increases wind speeds as it builds.
When winds reach 119km/h (74mph), it is known as a hurricane – in the Atlantic and Eastern Pacific – or a typhoon in the Western Pacific.
“Everybody has a plan until they get punched in the face. Well, we’re about to get punched in the face.”
Florida Mayor Bob Buckhorn, ahead of Hurricane Irma (2017)
The central eye of calmer weather is surrounded by a wall of rainstorms.
This eyewall has the fastest winds below it and violent currents of air rising through it.
A mound of water piles up below the eye which is unleashed as the storm reaches land.
These storm surges can cause more damage from flooding than the winds.
“Urgent warning about the rapid rise of water on the SW FL coast with the passage of #Irma’s eye. MOVE AWAY FROM THE WATER!”
Tweet from the National Hurricane Center
The size of hurricanes is mainly measured by the Saffir-Simpson scale – other scales are used in Asia Pacific and Australia.
Some minor flooding, little structural damage.
Storm surge +1.2m-1.5m
Roofs and trees could be damaged.
Storm surge +1.8m-2.4m
Houses suffer damage, severe flooding
Storm surge +2.7m-3.7m
Hurricane Sandy (2012) caused $71bn damage in the Caribbean and New York
Some roofs destroyed and major structural damage to houses.
Storm surge +4m-5.5m
Hurricane Ike (2008) hit Caribbean islands and Louisiana and was blamed for at least 195 deaths
Serious damage to buildings, severe flooding further inland.
Storm surge +5.5m
Hurricane Irma (2017) caused devastation in Caribbean islands, leaving thousands homeless
“For everyone thinking they can ride this storm out, I have news for you: that will be one of the biggest mistakes you can make in your life.”
Mayor of New Orleans Ray Nagin ahead of Hurricane Gustav, 2008
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