Puerto Rico is bracing for Hurricane Irma after the powerful storm caused at least seven deaths and left widespread destruction in the Caribbean.
The small island of Barbuda is said to be “barely habitable” while there were warnings of a “cruel” impact on French territories St Martin and St Barts.
Emergency efforts are being hampered by difficult access and communication with the hardest-hit areas.
Meanwhile, two other storms have strengthened to become hurricanes.
Irma, a category five hurricane, the highest possible level, is currently moving from the northern Virgin Islands, the US National Hurricane Center said.
The most powerful storm in a decade had wind speeds of 295km/h (185mph) and was expected to pass just north of Puerto Rico, then near or just north of the coast of the Dominican Republic on Thursday.
In Puerto Rico, Irma was already causing heavy downpours and strong winds.
Many residents have rushed to shops for water, food and other supplies, despite warnings to remain indoors. Officials have said that power could be cut off for several days.
Hurricane Irma first hit the dual-island nation of Antigua and Barbuda.
At least one death was reported on Barbuda, where Prime Minister Gaston Browne said about 95% of the buildings had suffered some damage.
“The island is literally under water. In fact, I’m of the view that, as it stands now, Barbuda is barely habitable,” he said after flying over the island, home to some 1,600 people.
However, Antigua, population 80,000, escaped major damage, with no loss of life, he said earlier.
Officials have confirmed at least six deaths and considerable damage in the French territories of St Martin and Saint Barthélemy – the French holiday destination popularly known as St Barts.
Power has been cut on both islands and emergency crews are still trying to reach the worst-hit areas.
St Martin’s airport, the third largest in the Caribbean, has been destroyed.
“I can already tell you that the impact will be hard and cruel, there will be casualties and the material damage on both islands will be considerable,” President Emmanuel Macron said.
Significant damage was also reported in the Dutch section of St Martin, known as Sint-Maarten.
US President Donald Trump said he and his aides were monitoring Irma’s progress.
“But it looks like it could be something that will be not good. Believe me, not good,” he told reporters at the White House.
It is still not yet clear what impact Hurricane Irma might have on the US mainland.