A deadly winter storm swept the eastern United States on Thursday spelling drudgery for millions and tragedy for a few, including an expectant mother killed by a snowplow.

US media counted at least 11 dead as a result of the storm, which dropped a thick blanket of snow over eastern cities overnight and shut down federal government operations in Washington.

One of the casualties was a 36-year-old pregnant woman, struck and killed by a snowplow in a New York parking lot.

Her baby was delivered alive by cesarean section but remains in critical condition.

Thousands of travelers were stranded as major air hubs such as Atlanta and New York, were closed down. Washington's Dulles International reported 14 inches (35 centimeters) of snow.

More than 6,000 flights were cancelled outright, and more than 3,000 delayed.

Nearly 800,000 homes and businesses lost power, mainly in Georgia and North and South Carolina.

As the storm moved north, the US National Weather Service warned that the "mammoth dome" of Arctic air would bring Arctic misery to communities from Georgia to New England.

In Washington, commuters woke to find their cars buried under a foot (30 centimeters) of snow, buses cancelled and city services struggling to keep even major roads open.

Schools were shut and the streets of the capital eerily deserted as federal workers stayed home or worked to scrape snow off sidewalks and driveways.

New York had an easier start but was forecast to receive a heavier covering as the storm churns up the east coast.

Meanwhile, "thundersleet" a foul mix of lightning storms and mixed precipitation, was brewing in Virginia and heading north.

Broadcasters fell over themselves to find superlatives to describe this "Snowmaggedon," dubbed "historic" and "mindboggling."

"This storm is dangerous. Road conditions are treacherous," said Governor Pat McCrory of North Carolina, a state where President Barack Obama had declared a federal emergency.

The storm is only the latest severe weather to hit the eastern United States in what was already the worst winter in 10 years.

But experts predicted it would have little long term economic impact, perhaps knocking only around 0.1 percent off first quarter GDP growth, according to economic Doug Handler of IHS Global Insight.

Although the storm would mean a short term drop in economic activity, consumers would spend more in heating fuel.

- Treacherous roads -

Snow slicked roads made commutes in the South agonizing, hours-long affairs, with the usually temperate cities of Raleigh and Charlotte transformed into ice- and snow-covered parking lots.

Hundreds of traffic accidents were reported and frozen roads hampered emergency response efforts.

Obama has declared states of emergency in several places in order to deploy federal resources to help deal with the frigid storm.

McCrory urged North Carolinians to stay indoors -- even if it meant sleeping at work -- rather than risk the treacherous roads.

"If you're in a safe warm place, stay in a safe warm place," McCrory told CNN. "We've already had two fatalities and we don't want to see more."

- Flights badly hit -

As the snow started blowing in overnight, temperatures hovered around 26 degrees Fahrenheit (minus three Celsius) but the bracing winds making it feel more like 15 degrees, forecasters said.

The White House cancelled its daily news briefing, and federal agencies told workers to stay home.

The Federal Emergency Management Agency said it had contacted state emergency offices in densely populated Maryland, Pennsylvania and Virginia to assess their assistance needs.

In addition to the FEMA aid, various localities across the region had readied emergency shelters at churches and recreation centers where residents could stay warm should they lose power.

Military personnel had also been mobilized, with more than 2,300 Army and Air National Guard pressed into action, according to a Pentagon statement.

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