At least 11 people were killed in the Dallas area from a storm system packing torrential rains and unleashing a string of tornadoes that toppled homes, cut power lines and snarled transport for people returning from the Christmas holidays.

The worst-hit area was in Garland, northeast of Dallas, where eight people were killed, cars blown off highways and homes flattened, officials said on Sunday.

Three other deaths were reported in the Dallas metro area, the nation's fourth most populous, with about 7 million people.

"It is total devastation," said Garland Police spokesman Lieutenant Pedro Barineau said. "It is a very difficult time to be struck by such a horrible storm the day after Christmas."

Five of the deaths in Garland were believed to have been related to vehicles having been struck by a tornado near State Highway 190 and Interstate 30.

More than 600 structures in North Texas suffered damage from the tornadoes and storms, officials said.

Six tornadoes were reported in Texas and one in Oklahoma on Saturday, the National Weather Service said.

The service has issued severe weather warning for large parts of the central United States on Sunday that include a blizzard warning for parts of New Mexico, Texas, Oklahoma and Kansas and a flash flood watch stretching from Texas to Ohio.

As of 8 am Central Time on Sunday, there were about 400 flights canceled in the United States, according to tracking service FlightAware.com, with more than half being in Dallas, a major US flight hub.

The weekend tornadoes follow a series that hit just before the Christmas holiday, mostly in the US South, and leaving at least 17 dead. - Reuters