Hurricane Gustav strengthened into a "dangerous" category three hurricane on Saturday as it approached the west of Cuba, the US National Hurricane Center in Miami said.
"Data from an Air Force reconnaissance aircraft indicate that Gustav continues to rapidly strengthen and now has maximum winds 185 kilometres per hour with higher gusts," it said.
That makes Gustav "a dangerous category three hurricane" on the five-category Saffir-Simpson scale -- equal in strength to Hurricane Katrina when it made landfall in the southern United States three years ago.
Gustav roared closer to Cuba in the early hours of Saturday after ripping through the Cayman Islands, Dominican Republic, Haiti and Jamaica -- leaving a total of 85 people dead in its wake.
The western Cuban province of Pinar del Rio and the Isle of Youth in the south were put on the highest level of weather alert.
Tens of thousands of people were asked to leave their homes in advance of the storm, which was expected to hit the western tip of Cuba -- where a fragile and aging housing stock is highly vulnerable to hurricanes -- later in the day.