- Bahamas Prime Minister Hubert Minnis confirmed the storm's death toll had risen to at least 20.
- People on Grand Bahama island were using jet skis and boats to pluck victims from homes flooded and pulverized by heavy rain and lashing winds from the monster storm.
- The United Nations said 70,000 people on Grand Bahama and Abaco islands were in "immediate need" of aid.
Bahamas Prime Minister Hubert Minnis on Wednesday lamented the "generational devastation" wrought by Hurricane Dorian, as he confirmed the storm's death toll had risen to at least 20.
The US Coast Guard and Britain's Royal Navy airlifted survivors and ferried in emergency supplies as flood waters receded in the Bahamas, while the weakened but still dangerous storm was "lashing" the coasts of the American states of Georgia and South Carolina.
The United Nations said 70,000 people on Grand Bahama and Abaco islands were in "immediate need" of aid while the prime minister confirmed the grim new victim count.
"There have been 20 confirmed deaths on Abaco. We expect that this number will increase," Minnis told a news conference.
He also issued a warning to looters, saying they will be prosecuted "to the fullest extent of the law" and announced the deployment of additional police and defence force officers.
Shelter, safe drinking water, food and medicine were urgently needed for some 50,000 people on Grand Bahama and between 15,000 and 20,000 on Abaco, UN emergency relief coordinator Mark Lowcock said after a meeting with Minnis.
"Speed is of the essence," Red Cross official Stephen McAndrew said of rescue operations on the two northernmost islands in the Bahamas archipelago which were pummelled by one of the strongest Atlantic storms on record.
People on Grand Bahama island were using jet skis and boats to pluck victims from homes flooded and pulverized by heavy rain and lashing winds from the monster storm.
US Coast Guard and Royal Navy helicopters were conducting medical evacuations, aerial assessments to help coordinate relief efforts, and reconnaissance flights to assess damage.
President Donald Trump spoke by telephone to the Bahamian leader and pledged US assistance, the White House said.
"A big section of the Bahamas was hit like few people have seen before," Trump said. "They need a big hand."
Aerial footage showed scenes of catastrophic damage in Abaco with hundreds of homes missing roofs, cars submerged or overturned, widespread flooding and boats reduced to matchwood.
Larry Lewis, who runs Paradise Watersports in the city of Freeport on Grand Bahama, said most of the flood waters had receded but some roads remained impassable.
"Everybody is trying to do their best," Lewis told AFP by telephone.
He said very few stores were open. "I saw a lot of people scrapping for something to eat," he said.
Roberto Smith, who was born in Abaco but now lives in Florida, said he was worried about his family.
"I spoke to my dad on the night of the hurricane, on Sunday night, and his roof blew up," Smith told AFP. "I haven't spoken to him since then. I am really worried. I can't even eat."
"The island is devastated," he added. "There is no power, no running water, no electricity."
The US Coast Guard said it had rescued 61 people including 19 injured patients from the Marsh Harbour clinic on Abaco island who were flown to Nassau on Tuesday.
USAID, the US relief agency, said meanwhile it was airlifting supplies such as plastic sheeting for shelter, hygiene kits and water from Miami.
A British landing ship, the RFA Mounts Bay, launched boats carrying supplies for Marsh Harbour on Abaco and Britain's Department for International Development said it had deployed a team of three humanitarian experts.
"The clock is now ticking to get help to those in need," British International Development Secretary Alok Sharma said.
The Bahamas, a former British colony, gained its independence in 1973 and is a member of the Commonwealth.
Dorian, which dumped as much as 30 inches of rain on the islands, was downgraded Tuesday morning to a Category 2 hurricane on the five-level wind scale. It was upgraded to a Category 3 storm late Wednesday as it bore down on the southeast US coast.
Dorian was packing maximum sustained winds of 115 miles per hour (185 kilometers per hour).
At 11:00 pm (0300 GMT Thursday), the NHC said Dorian was located 105 miles south of Charleston, South Carolina and moving north at around seven miles per hour.