OKLAHOMA CITY -- The death toll rose to six Wednesday from winter storms in the U.S. midsection that pushed toward the Northeast. More than 300 flights were cancelled in the storm's path.

Two passengers in a car on a sleet-slickened Arkansas highway died when the vehicle crossed the centre line and struck an SUV.

In Oklahoma, the Highway Patrol said a 76-year-old woman died Tuesday when a truck crossed into oncoming traffic and hit the car she was in. The Highway Patrol earlier reported that a 28-year-old woman was killed in another crash.

The storm's winds were also blamed Tuesday for toppling a tree onto a truck in Texas, killing the driver, and a tree onto a house in Louisiana, killing a man.

More than 325 flights around the U.S. were cancelled as of Wednesday morning, according to the flight tracker FlightAware.com. Most were at airports in the path of the storm.

Blizzard conditions were possible Wednesday for parts of Illinois, Indiana and Kentucky. By the end of the week, that snow was expected to move into the Northeast.

Thirty-four tornadoes were reported in Texas, Louisiana, Mississippi and Alabama during Tuesday's outbreak, the National Weather Service said. The storms left more than 100,000 in the region without power for a while, darkening Christmas celebrations.

Camera footage captured the approach of the large funnel cloud in Mobile, Alabama, the biggest city hit by numerous twisters.

A large section of the roof on the city's Trinity Episcopal Church was missing, said Scott Rye, a senior warden at the church.

On Christmas Eve, the church with about 500 members was crowded for services.

"Thank God this didn't happen last night," Rye said.