Forecasters say Hurricane Irene is bringing strong winds and rain to the northern coastlines of the Dominican Republic and Haiti as it continues to strengthen and take aim at the eastern United States.

Irene's center was passing just north of the two nations that share the island of Hispaniola on Tuesday, with maximum winds of 160 kilometers an hour. Dominican and Haitian authorities evacuated some residents from vulnerable areas ahead of the storm.

International aid agencies in Haiti also mobilized resources to help people affected by the storm in the impoverished nation, still struggling to recover from a devastating earthquake last year.

The U.S. National Hurricane Center says Irene is expected to become a major hurricane as it approaches the British territory of the Turks and Caicos Islands and the Caribbean nation of The Bahamas later Tuesday and Wednesday. Residents of both island chains were preparing for the storm's arrival.

The U.S. hurricane center says Irene could intensify further into a storm with winds of at least 210 kilometers per hour by Saturday, when it is expected to be near the coast of Florida. It predicts the storm will make landfall on Sunday over the U.S. states of South and North Carolina, potentially making it the first hurricane to hit the United States in three years.

The U.S. Federal Emergency Management Agency is urging people along coastal areas of the eastern United States to monitor the hurricane closely and prepare for severe weather later in the week.

Irene intensified into a hurricane over the U.S. territory of Puerto Rico before dawn Monday, flooding streets, knocking down trees and cutting power to about 1 million residents. There were no reports of serious injuries.

U.S. President Barack Obama declared an emergency in Puerto Rico late Monday, authorizing federal aid to help local authorities recover from the storm.

In other developments, lightning associated with Irene triggered a fire at the British Virgin Islands home of British tycoon Richard Branson. British actress Kate Winslet was visiting the residence at the time and carried Branson's 90-year-old mother to safety. No injuries were reported.