Hurricane Dorian battered the Bahamas with ferocious wind and rain on Sunday, the monstrous Category 5 storm wrecking towns and homes as it churned on an uncertain path toward the US coast where hundreds of thousands were ordered to evacuate.

There was no immediate word on casualties in the low-lying islands.

Packing sustained winds of 185 miles per hour (298 kilometers per hour), Dorian crashed onshore in the Abacos Islands, in the northwest of the Bahamas, as the strongest storm ever to hit the Caribbean chain. 

It was tied for the second most powerful hurricane ever in the Atlantic basin, the US National Weather Service said, with footage on social media showing major destruction from howling gusts of wind and pounding seawater.

Parts of the Abacos were ­under water as forecasters warned they faced a towering storm surge of 18-23 feet (5.5-7 meters). 

Winds were gusting over 220 miles per hour with no sign of weakening as the storm barreled west over the island of Grand Bahama, the National Hurricane Center in Miami said.

Video posted on the website of the Bahamian newspaper Tribune 242 showed water up to the roofs of wooden houses in what appeared to be a coastal town. Capsized boats floated in muddy brown water dotted with wooden boards, tree branches and other debris.

In other social media footage of what appears to be an inland area, cars were smashed or turned over, telephone poles and trees were snapped like twigs and debris filled the yards of severely damaged homes. AFP could not immediately confirm the authenticity of the footage.

After days of nerve-wracking uncertainty surrounding the storm's path, the southeastern US states of Florida, Georgia and South Carolina finally ordered coastal residents to evacuate in a mass exodus set to affect hundreds of thousands of people.

The NHC said the storm will be "dangerously close" to the Florida coast Monday night through Tuesday.

On Sunday night, the eastern part of Grand Bahama was experiencing the eye wall of the storm. The NHC said the situation on that island was life-threatening and would only worsen overnight.

"Do not leave your shelter as the eye passes over, as winds will rapidly increase on the other side of the eye," the NHC warned in its 02:00 GMT update.

Bahamas Prime Minister Hubert Minnis broke down in tears as he addressed a news conference, calling it "probably the most sad and worst day of my life," the Nassau Guardian reported.

"We're facing a hurricane... one that we've never seen in the history of the Bahamas," he said.

As of 02:00 GMT, the storm was 60 miles east of Freeport on Grand Bahama and moving slowly west.

"It feels like we are standing in a line waiting for a beating," Yasmin Rigby, a resident of Freeport, the island's main city, told AFP. 

A seemingly frantic post on the Facebook page of the fire department of Hope Town, a district of Abaco island, reported widespread destruction.