Hurricane Matthew has churned towards the Bahamas and Florida's east coast after killing at least 21 people in Haiti and prompting the hard-hit country to postpone a long-awaited presidential election.

The hurricane, the fiercest Caribbean storm in nearly a decade, whipped Cuba and Haiti with 230km/h winds and torrential rains yesterday, pummeling towns and destroying livestock, crops and homes.

In the United States, millions of people were urged to evacuate the southeastern coast and Florida Governor Rick Scott warned residents to prepare for a possible direct hit that could be catastrophic.

Hundreds of thousands of people had been evacuated from the path of the Matthew, which caused severe flooding and killed four people in the Dominican Republic as well as the deaths in Haiti.

The storm carved a path of devastation through western Haiti, dumping boats and debris on coastal roads hit by surging seas and heavily flooding residential areas.

Haiti, the poorest country in the Americas, had been set to hold a repeatedly-postponed presidential election on Sunday, but the country's electoral council delayed it again in the aftermath of Matthew.

No new date has yet been set.

Matthew was a Category 4 hurricane through yesterday but was downgraded to a still powerful Category 3 early today, the US National Hurricane Center (NHC) said.

The storm had sustained winds of about 195km/h this afternoon but the NHC said it could strengthen over warm waters as it approaches Florida.

The eye of the storm was about 113km south of Long Island in the Bahamas at 1800 GMT and was expected to be very near the east coast of Florida by tomorrow evening.

"Everyone in our state must prepare now for a direct hit," Florida Governor Scott told a news conference in Tallahassee.

"If Matthew directly impacts Florida, the destruction could be catastrophic and you need to be prepared."


It was difficult to assess the full extent of Matthew's impact in Haiti because it knocked out communications in many of the worst-affected areas, including the main bridge that links much of the country to the southwest peninsula.

Haiti was a particular concern because it is prone to mudslides due to extensive deforestation and tens of thousands of people are still living in tents and makeshift dwellings after the 2010 earthquake that killed more than 200,000 people.

A spokesman for UN Secretary-General Ban Ki-moon said the Haitian government estimated 350,000 people needed immediate assistance.

The death toll in Haiti included at least eight people killed by falling trees and six others swept away by swollen rivers, authorities said.

There were no immediate reports of deaths in Cuba, but Matthew devastated the picture-postcard tourist town of Baracoa, Cuba's oldest colonial settlement, in the province of Guantanamo.