Hurricane Sandy raged through the Bahamas today after leaving 21 people dead across the Caribbean, following a path that could see it blend with a winter storm and reach the US East Coast as a super-storm next week.

Sandy knocked out power, flooded roads and cut off islands in the storm-hardened Bahamas as it swirled past Cat Island and Eleuthera, but authorities reported no deaths in the scattered archipelago.

"Generally people are realising it is serious," said Caroline Turnquest, head of the Red Cross in the Bahamas, who said 20 shelters were opened on the main island of New Providence.

Sandy, which weakened to a Category 1 hurricane last night, caused havoc in Cuba earlier, killing 11 people in eastern Santiago and Guantanamo provinces as its howling winds and rain toppled houses and ripped off roofs.

Authorities said it was Cuba's deadliest storm since July 2005, when Category 5 Hurricane Dennis killed 16 people and caused 2.4 billion dollars in damage.

Sandy also killed one person while crossing Jamaica on Wednesday and 10 in Haiti, where heavy rains from the storm's outer bands caused flooding in the impoverished and deforested country.

Yesterday the hurricane's centre was about 185 miles east-south-east of Freeport, Bahamas. The storm had maximum sustained winds of 90mph and was moving north-north-west at 13mph.

Forecasters warned that Sandy would probably mix with a winter storm to create a monster storm in the eastern US next week whose effects will be felt along the entire Atlantic Coast from Florida to Maine and inland to Ohio.

Sandy, which crossed Cuba and reached the Bahamas as a category 2 hurricane, was expected to maintain its Category 1 storm status for the next several days.

In the Bahamas, power was out on Acklins Island and most roads there were flooded, government administrator Berkeley Williams said.

On Ragged Island in the southern Bahamas, the lone school was flooded.

"We have holes in roofs, lost shingles and power lines are down," said Charlene Bain, local Red Cross president. "But nobody lost a life, that's the important thing."

Steven Russell, an emergency management official in Nassau, said docks on the western side of Great Inagua island had been destroyed and that the roof of a government building was partially ripped off.

Sooner Halvorson, a 36-year-old hotel owner from Colorado who recently moved to the Bahamas, said she and her husband Matt expected to ride out the storm with their two young children, three cats, two dogs and a goat at their Cat Island resort.

On Great Exuma island, guest house operator Veronica Marshall supplied her only customer with a flashlight and some food before Sandy bore down. She said she was confident that she and her business would make it through intact.

"I'm 73 years old and I've weathered many storms," she said.

Tropical storm conditions were possible for Florida's south-eastern coast, the Upper Keys and Florida Bay by today.

Hurricane Sandy was expected to churn through the central and north-west Bahamas by this evening and then head northward off the US coast.

With storm conditions projected to hit New Jersey with tropical storm-force winds Tuesday, there was a 90 % chance that most of the US East Coast would get steady gale-force winds, flooding, heavy rain and maybe snow starting on Sunday and stretching past Wednesday, US forecaster Jim Cisco said.

In an announcement at the end of Cuba's Thursday night newscast, Cuban authorities said the island's 11 dead included a 4-month-old boy who was crushed when his home collapsed and an 84-year-old man in Santiago province.

Santiago, Cuba's second largest city near the eastern tip of the island, was spared the worst of the storm, which also slammed the provinces of Granma, Holguin and Las Tunas.

There were no reports of injuries at the US naval base at Guantanamo Bay in Cuba, but there were downed trees and power lines, said Kelly Wirfel, a base spokeswoman. Officials cancelled a military tribunal session yesterday for the prisoner charged over the 2000 attack on the navy destroyer USS Cole.

In Haiti, Joseph Edgard Celestin, a spokesman for the civil protection office, said the country's death toll stood at nine, including three people who died while trying to cross storm-swollen rivers in south-western Haiti.

Officials reported flooding across Haiti, where many of the 370,000 people still displaced by the devastating 2010 earthquake scrambled for shelter. More than 1,000 people were evacuated from 11 quake settlements, according to the International Organisation for Migration.

Sandy was also blamed for the death of an elderly man in Jamaica.

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