Bahamas leaders believe hundreds and perhaps thousands are missing in the archipelago nation of about 400,000 people in the wake of Hurricane Dorian.
Thousands of displaced people are living in "rapidly deteriorating" conditions in the worst-hit parts of the Bahamas six days after Hurricane Dorian made landfall, the UN World Food Programme warns.
The warning came as aid groups rushed emergency help to the storm-ravaged islands and officials said a death toll of 43 was likely to spike higher as the number of missing among the archipelago nation's 400,000 residents becomes clear.
Even as the aid ships and aircraft headed in, thousands fled the devastation, some abandoning hard-hit Great Abaco Island to seek safety in the capital, Nassau, and others heading to Florida for shelter, supplies and perhaps jobs.
Some 90 per cent of the homes, buildings and infrastructure in Marsh Harbour, where Dorian rampaged for almost two full days as one of the strongest Caribbean hurricanes on record, were damaged, the World Food Programme said.
It noted that thousands of people were living in a government building, a medical centre and an Anglican church that survived the storms, but had little to no access to water, power and sanitary facilities.
"The needs remain enormous," WFP spokesperson Herve Verhoosel said in an email on Saturday.
"Evacuations are slowly taking place by ferry, as hundreds of residents reportedly flee daily."
One of those who fled Abaco was 19-year-old Isaiah Johnson, who was staying in a hotel in Nassau with his mother and three sisters after the storm's 320km/h winds destroyed their homes.
A wealthy friend had paid for a two-week stay, but after that, it was unclear where they would go.
His mother was already searching for work in the US, Johnson said, reckoning that jobs would be hard to find in Nassau.
"Two weeks might be enough time for me to figure things out," Johnson said on Saturday. "For my mom, I'm not so sure."
A cruise ship with more than 1000 evacuees arrived in south Florida on Saturday.
The US Coast Guard and Navy were shipping in relief supplies and had already rescued some 290 people from isolated areas in the islands hit hard by the storm.
The US Agency for International Development said it raised its allocation of aid to the Bahamas by $US1 million ($A1.5 million), to $US2.8m ($A4.1m) in total and had moved enough emergency supplies for 44,000 people to the islands.
Some 70,000 people were in need of food and shelter, the WFP estimated, and private forecasters estimated that some $US3 billion ($A4.4 billion) in the insured property was destroyed or damaged in the Caribbean.
After pounding parts of North Carolina's Outer Banks Islands on Friday, a strengthened Dorian was headed towards Nova Scotia in Canada, where it was expected to make landfall by Saturday evening.
Its winds had picked up to 160km/h, meaning it once more rated a Category 2 on the five-step Saffir-Simpson scale of hurricane strength, the US National Hurricane Center said on Saturday.