Hurricane Irma damage considerable - Macron
Hurricane Irma has caused considerable damage on French island territories in the Caribbean, and casualties are expected, France's president says.
The impact of Irma on St Martin and St Barts would be "hard and cruel", Emmanuel Macron added.
His overseas affairs minister later confirmed at least two people dead and another two seriously injured.
The storm damaged more than 90% of buildings on Barbuda, Antigua and Barbuda's prime minister said.
The category five hurricane, the highest possible level, is now passing over the northern Virgin Islands.
The most powerful storm in a decade, with wind speeds of 295km/h (185mph), is also forecast by the US National Hurricane Center to pass near or just north of Puerto Rico, then near or just north of the coast of the Dominican Republic on Thursday.
Hurricane Irma first hit Antigua and Barbuda, before moving on to St Martin and Saint Barthélemy - the French holiday destination popularly known as St Barts.
Significant damage is also being reported in the Dutch section of St Martin, known as Sint-Maarten.
French Interior Minister Gérard Collomb said the hurricane had caused major floods, and destroyed buildings, including four of the "most solid" on the island.
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.
British Foreign Secretary Boris Johnson said the government was in touch with British overseas territories caught up in Irma, and was doing "everything we can to help those afflicted".
In the US, Florida's Key West area has ordered a mandatory evacuation, with landfall expected at the weekend.
The French government said earlier it was worried about thousands of people who had refused to seek shelter on the islands.
Officials in the French territory of Guadeloupe confirmed the following damage:
- On St Barts, the fire brigade station has been flooded with a metre of water, with engines out of service and crews sheltering on an upper floor; there is a total power blackout; many roofs have been blown off
- On St Martin, the prefecture building has been partially destroyed, with the prefect (chief officer) and 23 other people sheltering in a secure room; the fire station is out of order; there is a power blackout; several roofs at the police station have been blown off.