Melissa has already been blamed for at least four deaths in Haiti and the Dominican Republic this week, as its outer bands brought heavy rains and landslides.

The storm is moving at a worryingly slow pace -- just three miles (six kilometers) an hour -- which has meteorologists concerned that it will dump punishing rains on countries in its path for far longer than a storm that passes by more quickly.

The US National Hurricane Center (NHC) said that Melissa was packing maximum winds of about 140 miles (225 kilometers) per hour -- and would likely intensify into a top-level category 5 storm later Sunday.

Up to 40 inches (about a meter) of rainfall could hit parts of Jamaica, Haiti and the Dominican Republic, sparking flash flooding and more landslides.

"This extreme rainfall potential, owing to the slow motion, is going to create a catastrophic event here for Jamaica," NHC Deputy Director Jamie Rhome said in a webcast briefing.

"You need to just be wherever you're going to be and be ready to ride this out for several days," Rhome said.

"Conditions will deteriorate really, really rapidly here in the next few hours. Don't be out and about after sunset."

A 79-year-old man was found dead in the Dominican Republic after being swept away in a stream, local officials said Saturday. A 13-year-old boy was missing.

In neighboring Haiti, the civil protection agency reported the deaths of three people caused by storm conditions.

"You feel powerless, unable to do anything, just run away and leave everything behind," Angelita Francisco, a 66-year-old homemaker who fled her neighborhood in the Dominican Republic, told AFP through tears.

Floodwater had inundated her house, causing her refrigerator to float away as trash bobbed around the home.

- 'Remain in safe harbor' -

"Seek shelter now," the NHC advised residents of Jamaica. "Damaging winds and heavy rainfall today and on Monday will cause catastrophic and life-threatening flash flooding and numerous landslides before the strongest winds arrive."

The international airport in Kingston closed late Saturday to incoming and departing flights, Jamaican Transport Minister Daryl Vaz said.

Jamaican Prime Minister Andrew Holness advised fishermen to "remain in safe harbor." The Jamaica Information Service, a government agency, said Saturday that all seaports had been closed.

Melissa was expected to make landfall in Jamaica late Monday or early Tuesday, and then again in southeastern Cuba.

At 1500 GMT, the hurricane was located about 110 miles south of Kingston and 280 miles south-southwest of Guantanamo Bay, Cuba.

The Dominican Republic's emergency operations center has placed nine of 31 provinces on red alert due to risk of flash floods, rising rivers and landslides.

Melissa is the 13th named storm of the Atlantic hurricane season, which runs from early June to late November.

The last major hurricane to impact Jamaica was Beryl in early July 2024 -- an abnormally strong storm for the time of year.

Beryl brought downpours and strong winds to Jamaica as it moved past the island's southern coast, leaving at least four people dead.