Coastal residents in low-lying areas of Louisiana and Cuba are evacuating, while roads turn to rivers in Haiti’s capital, as twin hurricanes threatened the Caribbean and US Gulf Coast.

Marco strengthened to a hurricane on Sunday and is forecast to hit the Louisiana coast on Monday.

It will be followed by Tropical Storm Laura, now over the Dominican Republic, which is expected to travel across Hispaniola and Cuba and strengthen to a hurricane before striking the Gulf Coast on Thursday.

At least three people died, including a mother and her 7-year-old son, in the Dominican Republic due to collapsing walls.

Homes are washed away as torrential rain is dumped on communities in the Dominican Republic. Photo: Getty

Laura left more than a million in the country without electricity, forced more than a thousand to evacuate and caused several homes along the Isabela River to collapse.

Louisiana Governor John Bel Edwards on Sunday warned the state’s residents tropical storm-force winds would arrive by Monday morning and they should be ready to ride out both Marco and Laura.

“Wherever you are at dark tonight is where you need to be prepared to ride out these storms,” he said.

People selling from the market walk brave the flooded street in the neighbourhood of Pétion ville, Haiti. Photo: Getty

In Port-au-Prince, Haiti, videos on social media showed people wading waist-deep in muddy water in some of the worst flooding the capital has seen in years.

Haiti is especially vulnerable to intense rains due to shoddy infrastructure and deforestation increasing the likelihood of landslides.

Authorities called on residents along the Artibonite River to evacuate due to risks of the Peligre Hydroelectric Dam bursting its banks.

Haiti was first to report a death from Laura, where a 10-year-old girl was killed when a tree fell on her home in the southern town of Anse-a-Pitres.

With hopes dashed the mountains of Hispanola would weaken the storm, Cuba scrambled on Sunday to prepare for Laura.

A man tries to clear a passage in the flooded street in the neighborhood of Pétion ville, Haiti. Photo: Getty

Evacuations are underway in eastern parts of the Caribbean’s largest island, where the storm was expected to strike on Sunday evening, bringing flooding, before travelling along the entire island on Monday.

Back-to-back hurricanes arriving at the US coast within days “could result in a prolonged period of hazardous weather,” the National Hurricane Center warned.