Residents of Haiti's southwestern peninsula are bracing themselves for a long night of dangerous rain and catastrophic storm surges, as the strongest Caribbean storm in nine years began bearing down on the country.

Hurricane Matthew, a violent Category 4 storm packing 230k/h winds, was due to pound the western tip of Haiti early on Tuesday, according to the US National Hurricane Center.

"Life-threatening rain, wind and storm surges" had begun to spread over parts of the country as Matthew approached, the centre said in a 09:00 GMT advisory on Tuesday.

READ MORE: Hurricane Matthew storms towards Haiti and Jamaica

Haitians living in vulnerable coastal shacks frantically sought shelter as the outer bands of the cyclone had already reached the country's southwestern areas late on Monday.

Dozens of houses were flooded in the town of Les Anglais when the ocean rose, according to the local mayor, while strong winds caused power outages in Les Cayes, on the southern coast.

"We have gusts of wind hitting the whole area and the people have fled to a shelter," Les Anglais mayor Jean-Claude Despierre told Reuters news agency.

In Tiburon, another town nearby, authorities said people who had been reluctant to leave their homes also fled when the sea rose.

"Everyone is trying to find a safe place to protect themselves, the situation is very difficult," mayor Remiza Denize said, describing large waves hitting the town.

Matthew comes at a bad time for Haiti, the poorest country in the Americas [Andres Martinez Casares/Reuters]

The storm is forecast to spread hurricane force winds and up to three feet of rain across denuded hills prone to flash floods and mudslides, threatening villages as well as shanty towns in the capital Port-au-Prince.

"This is the most vulnerable suburb in the area. Here people are going about organising things, we know that the hurricane is coming," Afou, a volunteer at a children's home in the Cite Soleil slum in the capital, told Reuters.

"If things are bad then we will come together," said Afou, who only gave his first name. 

The Mayor of Cite Soleil, Frederic Hislain, said 150,000 people whose homes were threatened needed to be bused to safer places, but accepted that many people would not want to leave. Poor Haitians are often reluctant to leave home in the face of storms, fearing their belongings will be stolen.

The cyclone comes at a bad time for Haiti, the poorest country in the Americas and where 80 percent of the population lives in poverty.

Tens of thousands of people in the country still live in tents after a 2010 earthquake that killed more than  200,000 people.

Cholera introduced by UN peacekeepers is expected to rise in the October rainy season, and the country was due to hold a long-delayed presidential election on October 9.

The office of Interim President Jocelerme Privert said there was no change to the election date.

A general view of Kingston as Hurricane Matthew approaches Jamaica's capital [Henry Romero/Reuters]

Regional threat

Warnings and watches were in effect across the Caribbean, with five provinces of Cuba as well as parts of south-eastern and central Bahamas and Haiti under a hurricane warning.

Cuban authorities have evacuated about one million people from coastal regions, while the US Navy has ordered the evacuation of about 700 non-essential staff from its base at Guantanamo Bay.

Matthew is forecast to sweep over Cuba to the Bahamas on Tuesday and possibly reach the US state of Florida by Thursday as a major hurricane, though weaker than at present.

Florida Governor Rick Scott declared a state of emergency on Monday, designating resources for evacuations and shelters and putting the National Guard on standby.

Source: News Agencies