Hurricane Irma of `unprecedented intensity` in the Atlantic

Paris: Hurricane Irma is of "unprecedented intensity" in the Atlantic, meteorologists said Wednesday, as they advised residents of tiny Caribbean islands to take shelter as the massive storm approached.

The Category Five hurricane is set to strike the popular holiday destinations of Saint Martin and Saint-Barthelemy, with the French weather service warning of 12-metre (39-foot) swells and "extremely violent floods along the shore".

"Irma is a hurricane of unprecedented intensity in the Atlantic," said Meteo France, warning residents of the islands to stay indoors.

Meteo France said there would be a "major submersion of the low-lying parts of the coast", with the towns of Marigot and Grand Case on the Franco-Dutch island of Saint-Martin and Gustavia in French Saint-Barthelemy to "be particularly impacted".

The storm is expected to bring torrential rains, with 200-400 millimetres (8-16 inches) forecast.

Irma was continuing to strengthen, with gusts reaching 360 kilometres per hour (224 miles per hour) near the northern Lesser Antilles.