A freak snowstorm has swept across the American Mid-West, causing scores of traffic accidents and at least 12 deaths.

The unexpected white Christmas which descended from Missouri as far south as Texas snarled up roads and closed down airports, causing chaos as people headed home for the Christmas holidays.

They [road accidents] are coming in one right after another Corporal John Parrish Missouri Highway Patrol

Oklahoma, where such weather has not been seen for 25 years, was covered in snow up to 30 centimetres (12 inches) deep in places, and the storm is expected to move north by Christmas Day.

"All those people who wanted a white Christmas - we are going to give it to them," National Weather Service meteorologist Chuck Tingley said in Buffalo, New York, where up to 27 cm are forecast.

Missouri was hardest hit by the storm when it set in on Monday, with five people killed in four separate accidents on the roads.

"The crews are out trying to keep the roads clear but it's falling faster than they can plough it," said Susie Stoner of the state's Emergency Management Agency.

A traffic police spokesman who spoke to the St Louis Post-Dispatch said accidents were "coming in one right after another".

Tornado

So far, the storm has been blamed for three deaths in Oklahoma, three in Kansas and one in New Mexico.

Drivers in the Texas Panhandle found themselves in the novel situation of having to make their way through snow and there are reports of crashes there, too.

Christmas Eve in parts of Georgia and Alabama also saw stormy weather but no snow, as a tornado and heavy thunderstorms battered the southern states.