NASSAU — 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 defense 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 pummeled 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. — AFP