Hurricane Melissa: Seven people dead as world's strongest storm of the year rips through popular holiday destinations

The US National Hurricane Centre then expects Melissa to cross eastern Cuba and move over the Bahamas and Turks and Caicos by Wednesday.

The Category 5 storm's slow movement over unusually tepid Caribbean water had contributed to its ballooning size and strength, forecasters said, threatening Jamaica with days of never-before-seen catastrophic winds and as much as three feet of rain.

Melissa's wind-span is currently larger than the length of Jamaica and whose main airports sit very close to sea level.

Three people have died in Jamaica and 13 others have been injured while preparing for the hurricane, officials in the country confirmed.

Nearby Haiti and the Dominican Republic have already faced days of torrential downpours leading to at least four deaths, authorities in those island nations said.

Britons have been warned not to travel to Jamaica amid the storm.

Hours after ordering mandatory evacuations for parts of southern Jamaica, including the historic town of Port Royal, Jamaican Prime Minister Andrew Holness called on foreign support and warned of damage to farmlands, homes and infrastructure such as bridges, roads, ports and airports.

Despite warnings, some residents said they were reluctant to leave their homes for fear of looting and authorities said buses were waiting to be filled up and transport some 28,000 affected by mandatory evacuation orders.

"There is no infrastructure in the region that can withstand a Category 5," Mr Holness said.

The Jamaican leader said his government was as prepared as can be, with an emergency response budget of $33million and insurance and credit provisions for damage a little larger than those sustained from last year's devastating Hurricane Beryl.

Beryl was the earliest and fastest Atlantic hurricane on record to reach Category 5, but scientists warn that storms are becoming stronger faster as a result of climate change warming ocean waters, piling up fuel for seasonal storms.

"Tens of thousands of families are facing hours of extreme wind gusts above 100 mph and days of relentless, torrential rainfall," said AccuWeather Chief Meteorologist Jonathan Porter, adding infrastructure damages could hamper the arrival of aid.

"Slow-moving major hurricanes often go down in history as some of the deadliest and most destructive storms on record," he added.

"This is a dire situation unfolding in slow motion."

Jamaica has seen many large hurricanes in the past, including Category 4 Hurricane Gilbert in 1988, but a direct hit from a Category 5 would be unprecedented, said Evan Thompson, of Jamaica's Meteorological Service.

Melissa is moving much slower than Gilbert, Jamaica's last major direct hit, Mr Porter added, warning people should prepare to hunker down for days and some communities could be cut off for weeks.

Damian Anderson, a teacher from Hagley Gap, a town nestled in Jamaica's soaring Blue Mountains, said impassable roads had already cut off his community.

Mr Anderson said: "We can't move. We're scared. We've never seen a multi-day event like this before."