Melissa has reached hurricane strength as it nears Jamaica. The storm has already left at least three dead in Haiti and one in the Dominican Republic.

Deadly tropical storm Melissa has strengthened into a hurricane, the US National Hurricane Center (NHC) said Saturday as it barrels towards Jamaica.

"Melissa has become a hurricane with maximum sustained winds of 75 mph (120 km/h)," the NHC said. "Rapid intensification is expected, and Melissa is forecast to become a major hurricane tomorrow."

Forecasters have warned that the storm is expected to dump massive amounts of rain, which could lead to catastrophic flooding and landslides in the northern Caribbean region.

Melissa has already caused three deaths in Haiti. Two people were killed in a landslide on Thursday and a third died after a tree fell on them amid heavy rain earlier in the week.

A fourth person has been killed in the neighboring Dominican Republic, where another person remains missing.

Nearly 200 homes in the Dominican Republic have been destroyed, while water supply to more than half a million people has been disrupted.

In an update on Saturday afternoon, the NHC said Melissa was around 235 miles (380 kilometers) southwest of Haiti as it moved slowly towards Jamaica.

It is expected to bring torrential rainfall to Jamaica, as well as Haiti and the Dominican Republic, through to Monday.

Forecasters have warned of the possibility of dangerous floods and landslides.

Southeast Cuba is also expected to be hit and receive between 10 and 20 centimeters of rain.

Melissa is the 13th named storm of the Atlantic hurricane season, which runs from June 1 to November 30.

The US National Oceanic and Atmospheric Administration (NOAA) has predicted an above-normal season, with 13 to 18 named storms.

Scientists say that such extreme weather events are increasing in intensity and frequency as the atmosphere warms, owing largely to human fossil-fuel use.

Hurricane Melissa lashes Caribbean, raises flood threat