Nearly 25,000 people were evacuated from the Florida Keys area Sunday as tropical storm Fay approached Cuba, after sweeping over Haiti and the Dominican Republic.

The National Hurricane Centre in Miami said a hurricane watch was in place for Florida and Cuba, which means hurricane conditions were likely within 36 hours.

By Sunday evening the centre of the storm was located 335 kilometres southeast of Havana, Cuba and Fay was expected to move near Florida on Monday, the centre said.

There were steady evacuations starting Sunday morning from the Florida Keys, a low-lying 240-kilometre chain of islands.

On Saturday, Florida declared an emergency as it braced for the arrival of Fay.

Four people in Haiti and the Dominican Republic died in flooding caused by the storm as it spun toward Cuba.

Sustained winds of 75 kilometres per hour were recorded in the Dominican Republic. To become a hurricane, sustained winds must be at least 119 kilometres per hour .