More than 1,300 people have been sheltered at Red Cross camps in the US East Coast because of hurricane Irene, US authorities say.

Officials said on Saturday that the powerful storm would reach the towns along the New Jersey shore within hours, CNN reported.

Thousands of residents fled the coastal towns, including popular spots such as Atlantic City, Cape May and Long Beach Island.

Irene also knocked out power to some 500,000 customers across the eastern part of the country, according to officials.

Earlier on Saturday, the hurricane battered the coast of North Carolina near Jacksonville with winds of more than 85 mph (140km/h), the National Hurricane Center in Miami said.

Irene is approaching Washington, New York and Boston, a densely-populated corridor home to some 65 million people.

Meanwhile, New York City's mayor Michael Bloomberg urged 370,000 people to leave the city immediately, warning of serious threats of the hurricane.

Bloomberg has ordered the closure of the US subway system in New York City for the first time because of the natural disaster.