Hurricane Sandy has moved away from the coast of Cuba, taking aim at the central Bahamas with maximum sustained winds of 169 kilometres per hour.
Hurricane warnings have been posted for the southeastern Ragged Islands, the central Bahamas and the northwestern Bahamas.
Sandy is moving at approximately 30kph and remains a Category Two storm on the Saffir-Simpson scale of hurricane intensity, but it is expected to weaken over the next 48 hours as it moves through the Bahamas island chain.
A Category Two storm has winds between 154 and 177kph, leaving Sandy within a whisker of becoming a Category Three hurricane.
Sandy was forecast to drop below hurricane strength before making its expected US landfall, but as it will also likely move at a slower speed, the potential for damage may be increased as the storm drags out.
Heavy rains have been falling throughout the storm-stricken region, with forecasters predicting between six and 12 inches for most areas, and as much as 20 inches (50cm) in isolated places.
Local media in Cuba reported that roaring winds had left Santiago de Cuba, the island's second largest city, without power after the storm hit on Thursday.
Many trees were also toppled in the city, which is home to about 500,000 people and is located about 850km southeast of Havana, the Cuban capital.
At least 55,000 people had been evacuated ahead of Sandy, Cuban officials said, principally because of expected flooding.
The eye of the storm came ashore just west of Santiago de Cuba, with waves up to nine metres and a two metre storm surge that caused extensive coastal flooding, Jose Rubiera of the Cuban weather service said in a television report.
Thousands flee in Jamaica
Earlier, Sandy struck the Caribbean island of Jamaica, where it downed power lines and forced more than a thousand people to flee their homes.
Meteorologists at the US National Hurricane Centre said the storm was causing winds of up to 175kph and had become a "strong" category two hurricane by Thursday morning.
Citing police, meanwhile, local media in Jamaica reported that Sandy had claimed its first victim on Wednesday, killing a 74-year-old man who was crushed when a boulder rolled onto a house in Eastern St Andrew.
Schools and businesses were closed and authorities moved residents in low-lying, flood-prone areas into shelters as steady rain and winds pounded Jamaica.
Residents reported widespread power outages, flooded streets and some severely damaged homes.
"A part of the roof of my veranda just went like that," said 55-year-old Walford Freak, who lives in the coastal city of Iter Boreale. "At least five of my neighbours have lost their entire roofs."
The country's electricity provider said about 70 per cent of its customers were without power, due to the high winds and torrential rain.
"This is a very serious storm," Portia Simpson-Miller, the Jamaican prime minister, said earlier, after cutting short a visit to Canada and rushing home before the island's international airports closed.
"The government takes the threat seriously and I call on all Jamaicans to do likewise and prepare to face the enormous risks that this type of weather system can bring."
Police ordered a 48-hour curfew in major towns for safety and to deter potential looters, while slum dwellers in Kingston's sprawling shantytowns hunkered down as the storm moved north across the island.
The Office of Disaster Preparedness and Emergency Management said more than 1,064 people had moved into emergency shelters across the country, according to Jamaican daily The Gleaner.
The eye of the storm made landfall eight kilometres south of Kingston, which is home to one million of the island nation's 2.7 million inhabitants, at 3:00pm local time (19:00 GMT) on Wednesday.
At the time, the storm was causing winds of up to 129kph.
Gitmo hearing postponed
As heavy rain doused Cuba, some 1,700 people were evacuated in the country's Santiago de Cuba province as a precautionary measure.
"We cannot put a single human life in danger. We must evacuate people in areas we know are likely to be flooded, without losing time," Lazaro Esposito, a local civil defence official, told Cuban television.
The hurricane has also brought rough weather to the US naval base at Guantanamo where the US holds terrorism suspects.
The Pentagon said a preliminary hearing at Guantanamo involving the alleged al-Qaeda mastermind of the USS Cole bombing in 2000 was delayed until Thursday due to the storm.
In 2008, Cuba was hit by three hurricanes that caused a total of $10bn in damage and affected more than half a million homes.
Tropical Storm Gustav, which was less powerful than Hurricane Sandy, with sustained winds of 112kph, killed seven people in Jamaica in 2008.
Hurricane Ivan, a maximum category five on the Saffir-Simpson scale - and the sixth most intense Atlantic hurricane on record - killed 17 people and left 18,000 homeless when it smashed into Jamaica in September 2004.