Isabel is the first Atlantic storm to reach maximum intensity since Hurricane Mitch in 1998. The National Hurricane Center, a division of the National Weather Service, confirmed Isabel as a category five hurricane on the Saffir-Simpson storm scale from aircraft observations.

At 0300 GMT, Isabel's eye was about 515 kilometers (320 miles) north-northeast of the Caribbean's Leeward Islands, moving west-northwestward at a rate of 15 kilometers (nine miles) per hour, forecasters said.

Isabel was expected to continue on that trajectory over the next 24 hours. Satellite images indicate the storm may be weakening a little, a Hurricane Center update said.

"Large ocean swells and dangerous surf conditions are likely over portions of the Leeward Islands, the Virgin Islands and Puerto Rico over the next several days," it said.

The US State Department on Friday authorized its non-essential diplomats to leave the Bahamas and warned US citizens against visiting the islands due to damage that could be caused by Hurricane Isabel.

In addition, the department advised US citizens already in the Bahamas to consider leaving as the full-strength hurricane headed westward toward the central Antilles.

"The US State Department has given permission for non-emergency US personnel and family members of US personnel in the Bahamas to depart the Bahamas voluntarily," it said in a statement.

US citizens should "avoid travel to the Bahamas at this time due to the threat posed by Hurricane Isabel," it said. "US citizens in the Bahamas should consider departing until the storm has passed."

"If staying in the Bahamas, locate shelter, monitor media reports and follow all official instructions," the department said. "Visitors to the Bahamas should return to their hotels or cruise ships for further information and instructions."

TERRA.WIRE