A deadly ice storm stranded scores of people on slick roads and knocked out power to hundreds of thousands of US homes as winter-weary Americans dug in against Mother Nature's latest blow.

More than 3,700 flights due to take off Thursday were canceled across the United States because of the wintry blast, including well over half of flights at the busiest US airport, Atlanta's Hartsfield-Jackson International, airline monitors said.

Nearly half a million homes and businesses lost power, mainly in the southeast of the US, said CBS News, adding that at least 11 deaths had been blamed on the ferocious weather. CNN put the death toll at at least 10.

President Barack Obama declared states of emergency in Georgia and South Carolina in order to deploy federal resources to help deal with the frigid storm, just the latest to wallop the eastern half of the US since the start of the year.

The National Weather Service began warning days ago that a "mammoth dome" of Arctic air would form a "paralyzing ice storm."

"The ice accumulations remain mind-boggling, if not historical," it said.

The massive storm -- which stretched from Alabama to Virginia and had an estimated 100 million people in its path -- was expected to dump more than an inch (2.5 centimeters) of ice and as much as a foot of snow.

It was set to strengthen as it climbed northward along the eastern seaboard Thursday, with snowfall totals topping 18 inches by the time the storm reached the far northeastern New England region.

Accidents and abandoned cars caused massive traffic jams in North Carolina, with the usually temperate cities of Raleigh and Charlotte transformed into ice- and snow-covered parking lots.

North Carolina Governor Pat McCrory urged residents to stay indoors -- even if it means 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."

Many Atlanta residents stayed home, after the gridlock caused by a much weaker storm two weeks ago stranded thousands of people. It took days to clear the highway of abandoned vehicles at the time.

Speciality website FlightAware said airlines canceled at least 3,300 flights on Wednesday and had already shelved 3,703 flights for Thursday, including more than half of flights to and from New York and Washington.

"We expect that the number of cancellations will continue to rise as freezing precipitation hits major airports in Philadelphia, DC and New York," the service said.

The US capital's downtown was a virtual ghost town as snow blew in late in the evening, with temperatures hovering around 26 degrees Fahrenheit (minus 3 C) but the bracing winds making it feel more like 15 degrees, forecasters said.

The Federal Emergency Management Agency said it was in contact with state emergency offices in Pennsylvania, Maryland and Virginia to assess their assistance needs as the storm builds.

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

Power companies rushed out convoys of utility crews to trim tree limbs in advance of the storm's arrival, hoping to head off potentially massive cuts in power.

More than 230,000 customers lost power in South Carolina alone, local utilities reported.

The severe weather has also been playing havoc with US businesses and governments' bottom line.

Payrolls firm ADP said last week that the wintry onslaught has taken a toll on job growth.

Oil prices, by contrast, have been propelled higher by the extra-cold weather and succession of winter storms.

State and local governments are scrambling to cover the cost of clearing the snow, especially as road salt prices skyrocket amid shortages.

Farmers and rural residents are also facing high prices and shortages of the propane used to heat their homes and barns.