At least two people are dead as Hurricane Irma sweeps through the Caribbean, destroying buildings and causing flooding, officials say.
French overseas territories minister Annick Girardin said at least two people had been killed on the islands of Saint Martin and Saint Barthélemy.
"We're talking about two dead and two seriously injured for now. Obviously the situation can change very quickly," Ms Giradin said.
She said the French government was launching an emergency plan but it was vital to assess the damage because at these stage authorities could not get access to the worst-hit areas.
President Emmanuel Macron said earlier on Wednesday there were expected to be casualties on the islands.
"At this moment, it is too early to have a total figure, but I can already say that the impact will be hard and cruel," Mr Macron said after a crisis meeting to assess the situation.
"There will be casualties and the material damage on both islands will be considerable."
The French government had said it was worried about thousands of people who had refused to seek shelter on the islands as the powerful storm approached.
Irma has also destroyed buildings and caused major flooding on several French island territories in the Caribbean.
The Category 5 hurricane, the highest possible level, has sustained wind speeds reaching 295km/h.
French Interior Minister Gérard Collomb earlier said the four "most solid" buildings on Saint Martin, which is shared by France and the Netherlands, were destroyed.
Significant damage was also being reported in the Dutch section.
The most powerful Atlantic storm in a decade first hit Antigua and Barbuda, before moving on to Saint Martin and Saint Barthélemy - the French holiday destination popularly known as St Barts.
Its "extremely dangerous core" is forecast by the US National Hurricane Center to move over parts of the northern Virgin Islands on Wednesday, passing near or just north of Puerto Rico, then passing near or just north of the coast of the Dominican Republic on Thursday.
Thousands of people have been evacuated from at-risk areas across the Caribbean. Residents have flocked to shops for food, water, and emergency supplies, and airports have closed on several islands which are popular holiday destinations.
In the US, Florida's Key West area has ordered a mandatory evacuation, with landfall expected at the weekend.
There was no immediate news of possible casualties but officials in the nearby French territory of Guadeloupe confirmed that on St Barts, the fire brigade station had been flooded with a metre of water, there is a total power blackout and many roofs have been blown off
On Saint Martin, the prefecture building has been partially destroyed, the fire station is out of order, there is a power blackout and several roofs at the police station have been torn off.
Ms Girardin said the hurricane had caused major flooding in low-lying areas, and coastlines were being "battered extremely violently" by the sea.
Some 40,000 people live in the French part of Saint Martin, with around the same number estimated to live on the Dutch side. About 9000 people live on St Barts.
In the Dutch territory, known as Sint Maarten, the airport has been closed with photos showing debris strewn across the departures area and outside.
There has been a total power blackout, streets are littered with debris, cars are underwater and boats in the ports have been destroyed, Dutch broadcaster NOS reports (in Dutch).
France's interior minister said three emergency teams were being sent to the islands, two from France and one from Guadeloupe.
Photo: AFP Social media posts show flooding and damage on Saint Martin and, right, Puerto Rico resident Yanina Lopez takes shelter with her family.