Hurricane Sandy, having strengthened considerably since slamming into Jamaica earlier, has now hit southeastern Cuba, with winds of over 160km per hour cutting power lines and blowing trees over in the city of Santiago de Cuba.
Local media reported that roaring winds had left 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 750km 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 US National Hurricane Centre (NHC) said at 09:00 GMT on Thursday morning that Sandy, with maximum sustained winds of more than 160kph, was preparing to move off Cuba's northeastern coast.
The eye of the storm came ashore just west of the city, 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 toppled power lines and forced more than a thousand people to flee their homes.
Meteorologists at the NHC said the storm was causing winds of up to 175km per hour (kph) 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 Walford Freak, 55, 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 meanwhile 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 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.
Storm approaching Cuba
As the storm powered towards southeastern Cuba, it rapidly strengthened. The sustained winds were measured at 175kph, implying that Sandy was a strong category two hurricane.
Sandy was forecast to dump up to 12 inches of rain across Jamaica, eastern Cuba, Haiti and the Dominican Republic - with some isolated areas seeing totals as high as 20 inches.
"These rains may produce life-threatening flash floods and mudslides, especially in areas of mountainous terrain," the Miami-based NHC said.
On the forecast track, Sandy will move over portions of eastern Cuba overnight before heading to the Bahamas on Thursday and Friday. Tropical storm conditions were also forecast for Florida's east coast.
Michael Brennan, a hurricane forecaster at the NHC in Miami, said the storm's wind field was likely to extend 322km west from the center as it passed over the Bahamas, causing "very high surf and dangerous conditions all the way up the east coast into the [US states of North and South] Carolina".
Forecasters are not sure where it would go after that, with some computer models showing it could pose a risk to the US northeast early next week.
"It's too early to tell but there are some signs that have it hooking back towards the mainland as a wintertime 'nor-easter,'" said Brennan, referring to the powerful stormsthat can form in the north Atlantic at this time of year.
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 terrorims 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 112km per hour, 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.