Hurricane Irma, rampaging across the Caribbean, has produced sustained winds at 295 kilometres per hour (183 miles per hour) for more than 33 hours, making it the longest-lasting, top-intensity cyclone ever recorded, France's national weather service said Thursday.

"Such an intensity, for such a long period, has never been observed in the satellite era," which began in the early 1970s, said Etienne Kapikian, a forecaster at Meteo France.

"And it is continuing," he told AFP, adding that Irma would probably remain a Category Five storm at least until it hits the Bahamas.