SAN JUAN, Puerto Rico - Hurricane Irma, one of the most powerful Atlantic storms in a century, churned across northern Caribbean islands on Wednesday with a catastrophic mix of fierce winds, surf and rain en route to a possible Florida landfall this weekend.

Irma is expected to become the second powerful storm to thrash the US mainland in as many weeks after devastating Hurricane Harvey, but its precise trajectory remained uncertain on Wednesday.

The Category 5 storm's eye, packing winds of 295 km/h, passed over the island of Barbuda east of Puerto Rico, on Wednesday morning, the US National Hurricane Center in Miami reported. Its path could take it to Florida on Saturday.

"We are hunkered down and it is very windy ... the wind is a major threat," said Garfield Burford, the director of news at ABS TV and Radio on the island of Antigua, south of Barbuda. "So far, some roofs have been blown off."

Most people who were on Antigua and Barbuda were without power and about 1,000 people were spending the night in shelters in Antigua, Burford said.

"It's very scary ... most of the islands are dark, so it's very, very frightening," he said.

The amount of damage and the number of casualties were not known early Wednesday. A 75-year-old man died while preparing for the storm in Puerto Rico's central mountains, police said.

Several other Leeward Islands, including Anguilla, Montserrat, St. Kitts and Nevis, as well as the US and British Virgin Islands, Puerto Rico and Hispaniola, home to Haiti and the Dominican Republic, were under a hurricane warning.

"Preparations to protect life and property should be rushed to completion," the Hurricane Center said, warning that Irma "will bring life-threatening wind, storm surge and rainfall hazards" to those islands.

The Hurricane Center said Irma ranked as one of the five most powerful Atlantic hurricanes during the past 80 years and the strongest Atlantic basin storm ever outside the Caribbean Sea and Gulf of Mexico.

US President Donald Trump approved emergency declarations for Florida, Puerto Rico and the US Virgin Islands, mobilizing federal disaster relief efforts, the White House said.

Reuters - Ap