The death toll from Hurricane Melissa has risen to nearly 50 people, officials said, after the ferocious storm devastated Caribbean islands and was bearing down on Bermuda.

Flooding was expected to subside in the Bahamas although high water could persist in Cuba, Jamaica, Haiti and neighbouring Dominican Republic, the US National Hurricane Center (NHC) said on Thursday.

The storm, one of the most powerful ever recorded, was made four times more likely because of human-caused climate change, according to a study by Imperial College London.

Tropical storm conditions were occurring on Bermuda late on Thursday and the island was under a hurricane warning, with maximum sustained winds of 155 kilometres per hour, the NHC said.

Melissa smashed into both Jamaica and Cuba with enormous force, and residents were assessing their losses and the long road to recovery.

"The confirmed death toll from Hurricane Melissa is now at 19," including nine in Westmoreland and eight in St Elizabeth, both parishes in the Caribbean island's hard-hit west, Information Minister Dana Morris Dixon told local news outlets.

Communications and transportation access remains largely down in Jamaica and Cuba, and a comprehensive assessment of the damage could take days.

In impoverished Haiti, the country's civil defence agency said Thursday that the death toll had risen to 30, with 20 people injured and another 20 missing.

It said more than 1,000 homes have been flooded, with some 16,000 people in shelters.

In the east of the communist island of Cuba, battling its worst economic crisis in decades, people struggled through inundated streets lined with flooded and collapsed homes.

The storm smashed windows, downed power cables and mobile communications, and tore off roofs and tree branches.

Melissa "killed us, because it left us destroyed," Felicia Correa, who lives in the La Trampa community near El Cobre, told AFP.

"We were already going through tremendous hardship. Now, of course, we are much worse off."

Cuban authorities said about 735,000 people had been evacuated – mainly in the provinces of Santiago de Cuba, Holguin and Guantanamo.

The United States meanwhile has mobilised disaster assistance response teams and urban search and rescue personnel, and the teams were currently on the ground in the Dominican Republic, Jamaica and the Bahamas, according to a State Department official. Teams were en route to Haiti too.

The UK government announced £2.5 million in emergency funding for the region, and also said it was chartering "limited" flights to help British nationals leave.

In Jamaica, UN resident coordinator Dennis Zulu said Melissa had brought "tremendous, unprecedented devastation of infrastructure, of property, roads, network connectivity".

Hurricane Melissa tied the 1935 record for the most intense storm ever to make landfall when it slammed into Jamaica on Tuesday, according to the US National Oceanic and Atmospheric Administration. (AFP)