Hurricane Dorian has unleashed massive flooding across the Bahamas, pummelling the islands with so much wind and water that authorities urged people to find floatation devices and grab hammers to break out of their attics if necessary.

At least five deaths were blamed on the storm, that is heading to Florida.

“We are in the midst of a historic tragedy,” Prime Minister Hubert Minnis said, calling the devastation “unprecedented and extensive.”

The fearsome Category 4 storm slowed almost to a standstill as it shredded roofs, hurled cars and forced even rescue crews to take shelter until the onslaught passed.

Officials said they received a “tremendous” number of calls from people in flooded homes. A radio station received more than 2,000 distress messages, including reports of a five-month-old baby stranded on a roof and a grandmother with six grandchildren who cut a hole in a roof to escape rising floodwaters. Other reports involved a group of eight children and five adults stranded on a highway and two storm shelters that flooded.

Forecasters warned that Dorian could generate a storm surge as high as seven metres.

Police Chief Samuel Butler urged people to remain calm and share their GPS coordinates, but he said rescue crews had to wait until weather conditions improved.

“We simply cannot get to you,” he told Bahamas radio station ZNS.

Here’s the 6 pm EDT Tropical Cyclone Update: Extremely dangerous #Dorian continues to bring life-threatening conditions to Grand Bahama Island. The next intermediate advisory will be released by 8 pm. https://t.co/tW4KeFW0gB pic.twitter.com/x3cdXGzrsB

— National Hurricane Center (@NHC_Atlantic) September 2, 2019

On nearby Abaco Island, Parliament member Darren Henfield said he received reports of deaths but officials had not been able to confirm them.

Meanwhile in the United States, the National Hurricane Center extended watches and warnings across the Florida and Georgia coasts. Forecasters expected Dorian to stay off shore, but meteorologist Daniel Brown cautioned that “only a small deviation” could draw the storm’s dangerous core toward land.

By 5 pm local time on Monday (0700 Tuesday AEST), the storm’s top sustained winds fell slightly to 230 km/h. It was crawling along Grand Bahama Island at 2 km/h and then remained stationary.

The water reached roofs and the tops of palm trees. One woman filmed water lapping at the stairs of her home’s second floor.

Terrible news for Grand Bahama Island and another reason track is uncertain:

Since 1 PM, Dorian has drifted in nearly every direction except SE.

Latest movement is subtle SW drift. Wobbling like a spinning top. pic.twitter.com/BTdY0PzyAv

— Brett McIntyre (@BrettMcWx) September 2, 2019

Most people went to shelters as the storm neared. Tourist hotels shut down, and residents boarded up their homes. Many people were expected to be left homeless.

The Bahamas archipelago is no stranger to hurricanes. Homes are required to have metal reinforcements for roof beams to withstand winds into the upper limits of a Category 4 hurricane, and compliance is generally tight for those who can afford it. Risks are higher in poorer neighbourhoods that have wooden homes in low-lying areas.

-AAP