Hurricane Irene pounded the Bahamas Thursday en route toward the populous US east coast, punishing the nation of small islands with heavy rain and powerful winds.

Irene is a category three hurricane on the five-level Saffir-Simpson scale, and is forecast to strengthen to a category four storm with winds of 135 miles (217 kilometers) per hour by the time it reaches the US coast over the weekend.

In the latest forecast, meteorologists believe that Irene will creep up the south-eastern US coastline and graze land overnight Saturday to Sunday around Cape Hatteras, North Carolina.

The hurricane is then expected to continue its march just off the US coast and crash onto land near New York City on Sunday.

At 0900 GMT the US National Hurricane Center in Miami said the center of Irene, the first hurricane of the Atlantic storm season, was located about 130 kilometers east-southeast of Nassau, and some 1,180 kilometers (735 miles) south of Cape Hatteras, North Carolina.

The storm was packing winds of 115 miles (85 kilometers) per hour, and was moving towards the north-west at 19 kilometers (12 miles) per hour.

"On the forecast track, the core of the hurricane will continue to move over the northwestern Bahamas (Thursday), and pass well offshore of the east coast of central and north Florida (late Thursday) and early Friday," the NHC said.

In the Bahamas, a nation of 29 islands and hundreds of cays in the Atlantic ocean just north of the Caribbean, residents were preparing for the worst.

"My husband already started getting the shutters together, and we're also packing to get out," said Edna Smith, whose house in Holmes Rock, Grand Bahama, was flooded in the last hurricanes in 2004 and 2005. "We're not staying there. We're probably going to a shelter."

Deborah Rolle rushed to load groceries in the back of her car in Freeport after making last-minute purchases.

"I'm trying to get a jump-start on things, getting everything prepared," she said.

Up to 12 inches (30 centimeters) of rainfall were expected over the Bahamas, with an "extremely dangerous" storm surge up to 11 feet (3.3 meters) above normal tide levels, the NHC said.

Craig Fugate, the head of the US Federal Emergency Management Agency, urged residents all along the eastern US seaboard to get ready.

"This is going to be a big storm. Just because it hits one area doesn't mean its not going to cause damage further up the coast," he said.

Meteorologists said its tropical force winds extended out some 255 miles (410 kilometers).

US authorities began evacuating tourists from North Carolina's popular Outer Banks beach resort early Wednesday and ordered a mandatory evacuation of the Ocracoke and Hatteras barrier islands.

"This could be a very large storm storm, so we are taking it very seriously," said Governor Bev Perdue.

Bill Read, director of NHC, said the track remains uncertain but that "the exact center of the storm may stay close to the coast on Saturday and perhaps become a big threat to New England and Long Island."

Read said that the ocean's warm water was favorable for Irene to continue strengthening and growing over the next days.

"It's going to have a very large circulation as it moves north of the Carolinas," he said in a Wednesday press conference.

White House spokesman Josh Earnest said that President Barack Obama was briefed Wednesday on the hurricane during his vacation in Martha's Vineyard, Massachusetts, which coincidentally could be on or near the storm path in a few days.

He said officials "are looking at the very detailed logistical effort to ensure that we're going to have the proper resources pre-deployed."