Tropical Storm Laura brushed Cuba's southern coast Monday on its way to the United States, where officials predicted it would worsen to a hurricane ahead of its landfall after leaving 13 people dead as it ripped through the Caribbean.

"Gradual strengthening is expected, and Laura is forecast to become a hurricane by early Tuesday," the US National Hurricane Center said, predicting it would make landfall in the US state of Louisiana later in the week.

Meanwhile Storm Marco -- also headed to the Gulf of Mexico -- was downgraded from a hurricane overnight and was forecast to approach the coast of Louisiana later Monday, weakening to a tropical depression on Tuesday.

Marco's weakening winds have at least spared the Gulf what would have been twin hurricanes, unprecedented since records began 150 years ago.

Laura tracked westwards along the southern coast of Cuba on Monday, unleashing heavy rain and coastal flooding.

Winds gusting to 146 kilometers (90 miles) an hour hit the east of the island in the early hours, and waves of more than three meters (10 feet) battered the Maisi area of Guantanamo province.

The high winds tore tin roofs off homes and downed trees but local authorities reported no human casualties.

Cuban authorities had evacuated at least 160,000 people as a precaution in the provinces of Guantanamo, Santiago de Cuba, Granma and Camaguey.

Laura was expected to pass near the capital Havana on Monday afternoon before heading out to sea at dawn Tuesday.

"The center of Laura will move over the Caribbean Sea just offshore of the southern coast of Cuba this afternoon, cross western Cuba this evening, and move into the southeastern Gulf of Mexico overnight," the NHC said.

Deaths in the Caribbean

The Atlantic storm season, which runs through November, could be one of the busiest ever this year, with the Hurricane Center predicting as many as 25 named storms. Laura is the 12th so far.

Energy companies suspended some oil and natural gas production in the Gulf as the weather deteriorated.

Heavy rainfall and flash flooding also hit Jamaica and the Cayman Islands.

However, Storm Laura has done its worst damage so far in Haiti, killing nine people over the weekend.

The storm also killed four in the Dominican Republic's capital Santo Domingo, said the country's Center of Emergency Operations.

A woman and a child died at home, while a young man died when a tree fell on his home.

The storm flooded houses, cut off remote villages and left more than one million Dominicans in the dark.

In neighboring Haiti, a 10-year-old girl was among the nine dead as homes were flooded and evacuations were underway.

Storms pose a serious risk to Haiti every year from June to November. Even a heavy rainfall can threaten the country's poorest residents, many of them living in at-risk zones, near canals or ravines that can be obstructed by debris and quickly overflow.

A Petionville, near the capital Port-au-Prince, the damage caused by torrents of brown water rushing down from mountains was considerable.

"I didn't know there was (a) bad weather forecast. We don't often have electricity in my neighborhood so I couldn't follow the news on the radio," said Sony Joseph, shivering from the cold.