Updated 2.18pm

Hurricane Florence crashed into the Carolinas as a giant, slow-moving storm on Friday, threatening catastrophic flooding while leaving scores in need of rescue from rising waters and hundreds of thousands without power.

The centre of the hurricane's eye came ashore at about 0715 EDT near Wrightsville Beach close to Wilmington, North Carolina, with sustained winds of 90 miles per hour (150 kph), the National Hurricane Center (NHC) said.

North Carolina's governor, Roy Cooper, said Florence was set to cover almost all of the state in several feet of water.

National Weather Service forecaster Brandon Locklear predicted Florence would drop up to eight months of rain in two or three days.

There were no immediate reports of storm-related deaths or serious injuries, but authorities said more than 100 people were rescued further north in New Bern, where the downtown area of the city of 30,000 people was under water.

"WE ARE COMING TO GET YOU," New Bern city officials said on Twitter. "You may need to move up to the second story, or to your attic, but WE ARE COMING TO GET YOU."

More than 60 people, including many children and pets, were evacuated from a hotel in Jacksonville, North Carolina, after strong winds caused parts of the roof to collapse, local officials said. No one was hurt.

More than 370,000 people were without power in North Carolina early on Friday, state officials said. Utility companies said millions were expected to lose power and that restoring it could take weeks.

Thousands in shelters

Forecasters said the Category 1 storm's extreme size meant it could batter the US East Coast with hurricane-force winds for nearly a full day.

About 10 million people could be affected by the storm and more than 1 million were ordered to evacuate the coasts of the Carolinas and Virginia.

People walk on a local street as water from Neuse River starts flooding houses upon Hurricane Florence.

Almost 20,000 people had taken refuge in 157 emergency shelters, Cooper said.

There was a threat from tornadoes as Florence made landfall, the NHC said. South Carolina Governor Henry McMaster said the heavy rain could trigger landslides in the west of his state.

Storm surges could push as far as 2 miles (3 km) inland, NHC said, while heavy rains were forecast to extend into the Appalachian Mountains, affecting parts of Alabama, Tennessee, Kentucky and West Virginia.

Emergency declarations were in force in Georgia, South and North Carolina, Virginia, Maryland and the District of Columbia.

Still, some residents ignored calls to evacuate.

"I had a lot of fear initially but I'm glad to be inside and safe," said Zelda Allen, a 74-year-old retired tax accountant from Hampstead, North Carolina, who was riding out the storm at Wilmington's Hotel Ballast with her husband.

"I'm worried about what I might find when I go home, though," she said.