Millions leave homes and head inland after Hurricane Matthew threatens a 'direct hit'

The fiercest Caribbean storm in nearly a decade slammed into the Bahamas early on Thursday and was expected to intensify as it barreled towards the southeast US coast, where a mass exodus was under way in four states.

Roadways in Florida, Georgia and North and South Carolina were packed from late on Wednesday, with millions heeding warnings to flee inland as Hurricane Matthew approached, packing sustained winds of about 185 kilometers per hour, storm surges and heavy rain.

Matthew, which killed at least 26 people and damaged swathes of homes in southern Haiti, was predicted to strengthen from Category 3 to 4 storm en route to eastern Florida.

Landfall was expected there on Thursday night, the US National Hurricane Center said.

"Everyone in our state must prepare now for a direct hit," Florida Governor Rick Scott told a news conference on Wednesday. "If Matthew directly impacts Florida, the destruction could be catastrophic and you need to be prepared."

All four states in the hurricane's path declared states of emergency as shelters opened their doors after governors, along with President Barack Obama, urged residents to evacuate their homes.

About 12 million US residents were under hurricane watches and warnings, according to the Weather Channel.

Gas stations in Florida posted "out of gas" signs after motorists waited in long lines to fill up their tanks.

"Every gas station I went to is empty," said Charles Bivona in a Tweet late on Wednesday.

People who planned to wait out the storm stocked up on water, milk and canned goods, emptying grocery store shelves, footage from local media showed.

Residents and business owners boarded up windows and placed sandbags to protect against flooding.

"All boarded up and ready to bunker down. God be with us," West Palm Beach Florida resident Brad Gray tweeted.

A look at some of the most deadly hurricanes to hit the United States

In 2005, Hurricane Katrina left 1,800 people dead and was the costliest storm in US history with damage estimated at $108 billion. It was a Category 3 storm when it made landfall over Louisiana.

In 1938, roughly 700 people died in the Great New England Hurricane. It raked the region as a Category 3 storm and wiped out railroad tracks, utilities, homes, crops and the fishing industry, according to the National Weather Service.

In 1928, the Great Okeechobee Hurricane struck Florida as a Category 4 storm, leaving more than 2,500 dead. Lake Okeechobee overflowed, causing disastrous flooding that inundated several communities.

In 1900, a hurricane made landfall in Galveston, Texas, with winds estimated to be 209 kilometers per hour and a storm surge of a whopping 4.6 meters. Some 8,000 people died, and the National Oceanic and Atmospheric Administration says damage estimates exceeded $20 million at the time??roughly $700 million in today's dollars.

Allen Scurry (left), Brent Scurry (center) and Brandon Floyd, all of Lake City, South Carolina, install window shutters at an ocean front home in Garden City Beach. Randall Hill / Reuters