Miami: Ernesto grew into the first hurricane of the year yesterday as it gained strength rapidly on a path that could threaten the Caribbean and the Gulf of Mexico a year after Hurricane Katrina devastated New Orleans.

The US National Hurricane Centre said Ernesto's top sustained winds rose to 120kph, up from 110kph in a 5am advisory and 95kph just a few hours earlier.

The potentially dangerous storm was about 193km south-southwest of Port-au-Prince, Haiti, and was a Category 1 storm on the five-stage Saffir-Simpson scale of hurricane intensity.

A hurricane warning was issued for the southern coast of Haiti meaning hurricane conditions were expected within 24 hours.

Heavy rains and flooding were possible over much of the island of Hispaniola, home to Haiti and the Dominican Republic. The Miami-based hurricane centre said Ernesto could become a Category 2 hurricane the second-lowest level on the Saffir-Simpson scale before it reaches the coast of Cuba today.

A Category 2 storm has top sustained winds from 155-177kph and can cause moderate damage.

Jamaica, the Cayman Islands and Cuba issued hurricane watches as Ernesto approached.