Deadly cyclone Sandy crashes into US East Coast

One US sailor on board a replica of the HMS Bounty was recovered from the sea in an "unresponsive" condition and the captain was feared dead after the tall ship went down off the Carolinas.

The storm had already killed at least 67 people in the Caribbean as it came north, and American rescue services were braced for more casualties, as flood waters swamped parts of New York and cities further south.

Authorities warned the threat to life and property was "unprecedented" and ordered hundreds of thousands of residents from New England to North Carolina to evacuate their homes and seek shelter.

The National Hurricane Center said wind speeds inside Sandy dropped as the storm became a post-tropical cyclone, but remained hurricane-force at 80 miles per hour (130 kph) as it made landfall near Atlantic City, New Jersey.

Falling trees dragged down power cables, plunging millions of homes into darkness as night fell, while storm warnings cut rail links and marooned tens of thousands of travelers at airports across the region.

In New York, bystanders were awestruck as a massive tower crane snapped and dangled precariously from a skyscraper above a Manhattan street.

The hurricane technically became a post-tropical cyclone shortly before landfall as it collided with a wintry cold front descending from Canada.

While the coast faced the storm surge and heavy rain normally associated with hurricanes, this "Frankenstorm" hybrid system also triggered heavy snowfalls in the mountains of West Virginia and North Carolina.

"Hurricane-force winds are expected to gradually spread across southern New England and mid-Atlantic states from Connecticut southwards to New Jersey and Delaware," the National Hurricane Center warned.

"The combination of an extremely dangerous storm surge and the tide will cause normally dry areas near the coast to be be flooded by rising waters."

Barometric pressure in the heart of the storm dropped to only 940 millibars, on course to break records for low pressure in the region.

"The most important message to the public I have right now, is 'please listen to what your state and local officials are saying.' When they tell you to evacuate, you need to evacuate," President Barack Obama said.

Disaster estimating firm Eqecat forecast that Sandy would affect more than 60 million Americans, a fifth of the population, and cause up to $20 billion (15 billion euros) in damage.

Refineries closed and major arteries such New York's Holland Tunnel were shut to traffic. The operator of two major New Jersey nuclear plants said they might have to be closed, threatening half the state's power supply.

The New York Stock Exchange, the Nasdaq and the futures markets in Chicago were closed for Monday and Tuesday, along with federal government offices and the entire Amtrak rail network on the eastern seaboard.

New York, Boston and Washington DC were effectively shut for business and -- with just eight days to go until polling day -- the US presidential election campaign was severely disrupted.

Streets leading up to Atlantic City's famed ocean-front boardwalk were flooded, and mostly deserted as the city braced for high tide. In nearby Ocean City, a section of promenade was smashed and fell into the storm surge.

Obama cancelled an appearance in the swing state of Florida, returning to the White House to steer the relief effort.

"The election will take care of itself next week," Obama said. "Right now, our number one priority is to make sure that we are saving lives... and that we respond as quickly as possible to get the economy back on track."

Both the Democrat incumbent and his Republican rival Mitt Romney were keen to display resolute leadership in the face of the storm, given the memory of Hurricane Katrina in 2005. Romney also cancelled some appearances.

Former president George W. Bush was widely seen as having bungled the handling of Katrina, which devastated New Orleans. The failure of authorities in the ensuing emergency response tainted the rest of his presidency.

Obama has signed emergency declarations to free up federal disaster funds for New York state, Massachusetts, Connecticut, Maryland, the District of Columbia, New Jersey, Pennsylvania and Rhode Island.

"There will undoubtedly be some deaths," Maryland governor Martin O'Malley told reporters, citing the intensity of the storm and likely floods caused by the tidal surge and high waves.

A Maryland motorist died in a road accident as the winds and rain lashed the state but officials would not directly link it to the foul weather.