NASSAU, Bahamas — Hurricane Dorian unleashed massive flooding across the Bahamas on Monday, pummeling 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.

"We are in the midst of a historic tragedy," Bahamian Prime Minister Hubert Minnis said in announcing the fatalities. He called 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 5-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.

The deaths in the Bahamas came after a previous storm-related fatality in Puerto Rico. At least 21 people were hurt in the Bahamas and evacuated by helicopters, the prime minister said.

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.

Forecasters warned that Dorian could generate a storm surge as high as 23 feet (7 meters).

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 8 pm EDT Monday, the storm's top sustained winds had fallen to 140 mph (220 kph), still within Category 4 range. It was virtually stationary, centered just 25 miles (40 kilometers) northeast of Freeport. Hurricane-force winds extended outward as far as 45 miles (75 kilometers) from the center The water reached roofs and the tops of palm trees. One woman filmed water lapping at the stairs of her home's second floor.