Irma on Tuesday intensified into an extremely dangerous Category 5 hurricane on the Saffir-Simpson wind scale, the US National Hurricane Center (NHC) said in its latest advisory.

Hurricane Irma is about 270 miles (440 km) east of Antigua and packing maximum sustained winds of 175 mph (280 km/h), the Miami-based weather forecaster said.

Irma, which is forecast to remain a powerful category 4 or 5 hurricane during the next couple of days, will move near or over portions of the northern Leeward Islands Tuesday night and early Wednesday, the NHC said.