Irma picked up strength and has become an "extremely dangerous" Category Five hurricane as it approached the Caribbean on Tuesday, the Miami-based National Hurricane Center reported.

"Preparations should be rushed to completion in the hurricane warning area," the NHC said in its 1200 GMT bulletin.

The monster hurricane, the most powerful of the five-level Saffir-Simpson scale, is about 270 miles (440 kilometers) east of the island of Antigua packing maximum sustained winds of 175 miles (280 kilometers) per hour.