As it girded for its share of the region's worst storm in nearly a decade -- perhaps a direct hit as early as Thursday -- the Bahamas closed its main international airport and Nassau's port.
Haiti and the eastern tip of Cuba -- blasted by Matthew on Tuesday -- began the messy and probably grim task of assessing the storm's toll.
Cuba said a historic colonial town was devastated. Haiti postponed a presidential election that was scheduled for Sunday.
Matthew hit those two countries as a Category Four hurricane but has since been downgraded to three, on a scale of five, by the US National Hurricane Center.
Bahamian Prime Minister Perry Christie urged people living on the southern coasts of the tourist-dependent islands to evacuate.
"Seriously consider now moving to higher grounds. Natural phenomena can be violently unpredictable," Christie said.
Haitian officials struggled to assess damage because the south of the country, where the storm made landfall, has been largely cut off by the collapse of a key bridge.
The United Nations office for coordinating humanitarian affairs said fully half of Haiti's population of 11 million are expected to be affected in one way or another.
Across the region more than 600,000 people are living in emergency shelters, more than half of them in Haiti, the UN office said.
At least 350,000 people in Haiti need immediate assistance, Secretary General Ban Ki-moon's office said, quoting the Haitian government.
Cuba said it had no fatalities to report but that four cities in the east were cut off because roads were blocked by large chunks of rock hurled by the storm.
Farther to the north, storm preparations gathered pace in Florida and other US coastal states. Parts of North Carolina and Georgia have declared states of emergency.
"This is something to take seriously. We hope for the best, but we want to prepare for the worst," President Barack Obama said in Washington.
As #HurricaneMatthew takes aim at Bahamas and Florida we answer, "What is a hurricane?" https://t.co/A6sXe5nxqO pic.twitter.com/wul1ZV72xL — AFP news agency (@AFP) October 5, 2016
A 'direct hit'
Homeowners in Miami and other cities flocked to hardware stores for plywood to board up their windows and other essentials like water, flashlights and batteries. The storm was expected to be near Florida's coast Thursday evening.
People living on barrier islands and in flood-prone areas were urged to leave.
"Everyone in our state must prepare now for a direct hit from Hurricane Matthew," Governor Rick Scott warned. "If you're able to go early, leave now."
In South Carolina, more than one million people living on the coast were under orders to evacuate, starting at 3 pm (1900 GMT). But traffic on highways leading inland was already reported to be bumper to bumper hours ahead of time.
Matthew's overall death toll stood at nine -- five in Haiti and four in the Dominican Republic -- but was certain to rise as the storm bruises its way north.
'Extremely dangerous'
Matthew made landfall in Haiti shortly after daybreak Tuesday as an "extremely dangerous" Category Four storm near the southwestern town of Les Anglais, packing top winds of around 230 kilometers per hour, the NHC said.
It marked the first time in 52 years that a Category Four storm made landfall in Haiti.
The storm was expected to move across the Bahamas through Thursday and near the coast of Florida Thursday evening, the NHC said.
A tropical storm warning remained in effect for Haiti, as did a full blown hurricane warning for Cuba's eastern provinces.
Matthew was forecast to dump 38 to 63 centimeters (15 to 25 inches) of rain over southern Haiti with up to a meter possible in isolated areas, and has been blamed for triggering mudslides.
The country is home to almost 11 million people, with thousands still living in tents after the massive earthquake in 2010.
Erosion is especially dangerous because of high mountains and a lack of trees and bushes in areas where they have been cut for fuel.
Schools will remain closed until Monday.
Officials reported significant flooding and waves up to five meters (16 feet) in coastal villages in the east of Cuba.
Cuban authorities evacuated some 1.3 million people.
The storm left a trail of destruction in Baracoa, the first Spanish settlement in Cuba.
"There's nothing left of Baracoa. Just debris and remains," said resident Quirenia Perez, 35, speaking to AFP by cell phone after losing her roof, electricity and land line in the storm.
She added: "The big colonial houses in the city center, which were so pretty, are destroyed."
