Media playback is unsupported on your device Media caption Michael Bloomberg: ''The time for evacuation is over''

Hurricane Irene is pummelling the US east coast after making landfall in North Carolina.

At least eight people have been killed in North Carolina, Virginia and Florida, as Irene sweeps north.

The 500-mile wide storm, with winds of around 80mph (129km/h), is moving slowly northwards. New York and other large cities are in its predicted path.

More than two million people have been ordered to leave their homes after warnings of storm surges and flooding.

New Jersey Governor Chris Christie announced on Saturday afternoon that "over a million people have left the Jersey shore in the last 24 hours".

In New York City, 300,000 people living in low-lying areas have been told to leave in an unprecedented mandatory evacuation.

Mayor Michael Bloomberg said those who had not evacuated should now stay put until the storm had past.

"The edge of the hurricane is finally upon us," he told reporters.

"The time for evacuations is over. At this point, if you haven't evacuated, our suggestion is you stay where you are."

More than 90 shelters with room for about 70,000 people have been opened in New York but by early evening on Saturday only about 5,500 people had checked in.

Media playback is unsupported on your device Media caption The streets of New York are empty

New York's entire transit system of subways, buses and commuter rails stopped running at midday on Saturday - the first time officials have closed the network because of bad weather.

It was not expected to reopen until at least Monday. Airports are also closing.

Energy firm Con Edison also shut down miles of steam pipes under the city to prevent explosions if they come into contact with cold water.

President Barack Obama, who cut short his holiday to return to Washington, had a conference call about the hurricane with emergency officials on Saturday.

He earlier warned Irene could be "a historic hurricane" and that everyone should take the storm seriously.

The National Hurricane Center has downgraded Irene from a category two to a category one hurricane but says winds gusting up to 90mph extend outwards some 90 miles from the eye of the storm. Tropical-force winds extend as far as 290m.

The NHC expects Irene to weaken after hitting North Carolina, but it is forecast to remain a hurricane as it moves north along the Atlantic coast on Sunday.

Irene remains a "large and dangerous" storm, US Homeland Security Secretary Janet Napolitano warned on Saturday.

'Dangerous surges'

The eye of the storm crossed the North Carolina coast near Cape Lookout at about 0730 local (1130 GMT) on Saturday - at the start of what is predicted to be a 36-hour assault on the US east coast.

Power lines have been toppled and more than 600,000 people are without electricity in North Carolina and neighbouring Virginia.

"Extremely dangerous" storm surges have been forecast in some areas that could raise water levels by up to 11ft (3.35m).

Residents hoping to ride out the storm have stocked up on food, water and fuel.

"There's nothing you can do now but wait. You can hear the wind and it's scary," one man who rode out the storm told the Associated Press.

"Things are banging against the house. I hope it doesn't get worse, but I know it will. I just hate hurricanes," said Leon Reasor in the Outer Banks town of Buxton.

In New York City, parts of Manhattan and into Staten Island are at particular risk, according to projections issued by city authorities.

Hospitals in affected areas have evacuated patients.

In Washington DC, Sunday's dedication of the new memorial for Martin Luther King Jr - which President Obama had been expected to attend - has been postponed until at least September. The power company serving the Washington area warned of "potential widespread power outages" at the weekend.

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Supermarkets along the east coast were reportedly running out of supplies as people stock up before the storm arrives.

The Pentagon has loaded 200 trucks with emergency supplies, and 100,000 National Guard troops are on standby.

The American Red Cross said it was preparing dozens of emergency shelters along the east coast.

The north-eastern seaboard is the most densely populated corridor in the US, with more than 65 million people living in major cities along the coast from Washington DC in the south to Baltimore, Philadelphia, New York and Boston further north.

States of emergency have been declared in North Carolina, Maryland, Virginia, Delaware, New Jersey, New York and Connecticut.

"We're going to have damages, we just don't know how bad," Craig Fugate, head of the US Federal Emergency Management Agency, told the Associated Press news agency.

"This is one of the largest populations that will be impacted by one storm at one time."

If Irene hits New York and New England at category two, it will be the region's strongest storm since Hurricane Bob glanced off Massachusetts in 1991, and Hurricane Gloria, which caused extensive damage to New York City in 1985.