Hurricane Ike has powered ashore south of Cuba's capital, Havana, bringing with it fierce winds and heavy rains, reported BBC.
Huge waves are pounding the capital's seafront promenade as the eye of the storm moves closer, while there are floods and mudslides on higher ground.
Tens of thousands of people have been evacuated from Havana ahead of the storm's second landfall this week.
Four people are known to have died so far in the storm, which battered the east of the island on Monday.
It is the first time in several years that a hurricane has claimed lives in Cuba, which is renowned for its well-organised mass evacuations.
One person was killed by a falling tree, an elderly woman died when her house collapsed and two others were electrocuted.
State television said almost 1.25 million people had been moved to shelters so far - more than one tenth of the island's population.
A further 175,000 people were evacuated from Havana; particularly those living in unstable apartment blocks that may not be able to withstand a direct hit by hurricane-force winds.
The Cuban authorities have put the entire population on maximum alert.
The eye of the storm made its second landfall in Cuba's Pinar del Rio province, about 55 miles (88km) south-west of Havana, packing sustained winds of 80mph (130km/h).
The Category One storm was moving west-north-west at 13mph, the US National Hurricane Center (NHC) said.
President Raul Castro and his brother Fidel were monitoring the storm "minute by minute", state television said.
The BBC's Michael Voss in Havana says it is still too early to tell the full extent of the economic impact wrought by Ike.
Tens of thousands of buildings have been damaged and crops destroyed.
Ike first struck in Holguin province, which is home to the nickel mines, the country's top export earner. There is also likely to be an impact on the tourist industry, our correspondent says.
The storm is due to head out into the Gulf of Mexico in a few hours' time, where it is expected to pick up speed with a projected heading towards the US Gulf coast.
Louisiana's governor has warned coastal residents to be prepared to move inland, although the NHC said it was still too early to tell in which direction Ike would move.
The United Nations cultural agency, Unesco, has offered to help the Cuban government make good any damage to heritage sites and important buildings in Havana.
The agency's director in Havana, Herman van Hooff, said that the latest storm could be a setback to restoration work.
"Since the [1990s] there has been a very strong management system in place for the old Havana area, and a lot has been restored since then.
"There is still a lot of fabric, a lot of architecture, a lot of housing that is in a fragile state, so any impact by a hurricane, be it wind or rain, is a great concern to everybody," he told the BBC.
Among those evacuated from Cuba before the arrival of Ike were 15,000 tourists.
Cuba is still reeling from the effects of Hurricane Gustav, which hit just over a week ago, damaging almost 100,000 homes in the west of the island.
Ike earlier caused 66 deaths in Haiti and reportedly damaged 80% of the homes in the Turks and Caicos Islands.
Haiti, the poorest country in the Western hemisphere, has endured the onslaught of four tropical storms in a three-week period, causing more than 550 deaths.