"Attention Havana, attention Havana. Havana is on hurricane alert. All residents must strictly follow the instructions of the civil defence," local radio stations broadcast.
Officials said at least 1.5 million people had been evacuated from vulnerable areas in Cuba, which is also recovering from the strike by Hurricane Gustav last week on western provinces.
Cuban television said four people were killed by Ike-related incidents, including two men who were electrocuted when they tried to take down an antenna that fell on to an electric line.
|Ike smashed into Cuba's eastern
coast on Sunday [AFP]
A woman was also killed when her house collapsed and a man crushed when a tree blew over and on to his home.
Hurricane deaths are rare in Cuba where the government carries out mass evacuations.
Ike was expected to hit the US in the eastern part of the state of Texas after ploughing through the Gulf of Mexico, although there were fears that Louisiana, still recovering from the impact of Hurricane Gustav, could also be affected.
Energy companies which halted production during the impact of Gustav have delayed restarting the flow of oil under the threat posed by Ike.
The US National Hurricane Centre also warned that Ike could strengthen again as it headed toward the Gulf of Mexico.
Ike had earlier ripped through the southern Bahamas and the Turks and Caicos islands, as well as Haiti.
Officials said at least 66 people, including more than a dozen children, had died from the floods brought by Ike in Haiti, in addition to the 500 killed last week by Tropical Storm Hanna less than a week ago.
Eighty per cent of homes in the Turks and Caicos islands were damaged by winds, although there were no reports of deaths.
Ike has also ripped off roofs and knocked over trees and power lines in the Bahamas' southernmost island of Great Inagua.