WASHINGTON (AFP) - Irma has intensified into a Category 3 hurricane in the eastern Atlantic, just days after Harvey, the first major storm of the season, unleashed massive rain and floods on Texas and Louisiana, US meteorologists said on Thursday (Aug 31).

Irma churned in open waters off the west coast of Africa, packing winds of 185km per hour, the Miami-based National Hurricane Centre said in its advisory.

The storm is currently far from land, but is heading straight toward the southern Caribbean, to the area between the US island territory of Puerto Rico and South America's northern coastline.

Irma is forecast to reach the Lesser Antilles islands in the Caribbean early next week.

South Florida meteorologist Craig Setzer said it was far too early to tell if the storm would impact Florida or the Gulf of Mexico.

Anxiety is running high over the risk of another storm in the southern United States after Harvey pounded the US Gulf Coast, making landfall on Friday as a Category Four hurricane.

Now that Irma has reached Category three status, it is the second major storm of the Atlantic season.

Irma gathered strength quickly, rising to hurricane status less than 24 hours after forming as a tropical storm.