By Suzi Parker
LITTLE ROCK, Ark., April 27 (Reuters) - Tornadoes ripped through the south-central United States on Sunday, killing at least 12 people in Arkansas and Oklahoma and wiping out entire neighborhoods, authorities said as rescue workers searched in darkness for survivors.
Winds ripped houses off their foundations and flipped cars on top of the rubble in the small town of Vilonia in central Arkansas' Faulkner county, one of the worst-hit communities, television pictures showed.
Arkansas authorities said at least two people had died in Vilonia, three in other parts of Faulkner and six more across the state - the first reported casualties of this year's tornado season. Another death was reported in neighboring Oklahoma.
Searchers were continuing to dig through rubble in Vilonia and a spokesman for the County Sheriff's office said there was a "mass casualty situation".
"An entire neighborhood of 50 or so homes has been destroyed. Many homes are completely gone except the foundation ... There is more devastation like this in other parts of Arkansas," U.S. Representative Tim Griffin told Reuters.
Cable television's Weather Channel showed videotape of mangled, overturned cars, some with people still inside, lining miles of Interstate 40 near Mayflower, 22 miles (35 km) northwest of state capital Little Rock.
Motorists searched crushed vehicles for victims while others stood dazed on the road. Authorities closed the route.
A tornado hit the east side of Mayflower at around 7.30 pm, killing at least one person, tearing up trees and bringing down power lines, making it difficult for the emergency services to find stricken areas in the dark, officials there said.
"It's extremely hazardous here right now," said Will Elder, an alderman in the city. "The power lines are down, roads are blocked and they will have to proceed with caution."
The Arkansas National Guard was deployed to help out in the state.
An aide to Arkansas Governor Mike Beebe said five people had died in both Faulkner and Pulaski counties, with another fatality reported in White County.
Brandon Morris, a spokesman for the Arkansas Emergency Management Agency, said Mayflower and Vilonia appeared to have been the hardest hit communities.
At least one person was killed in a tornado a small town in the northeast corner of neighboring Oklahoma, according to Ottawa County Sheriff's Department spokesman Derek Derwin.
Media and the National Weather Service reported that two people were killed.
That twister was spotted in Quapaw, 200 miles (322 km) northeast of Oklahoma City at about 5:45 p.m., according to the weather service. An Ottawa County, Oklahoma, police dispatcher said a search and rescue effort was under way in Quapaw, but could not confirm reports of fatalities.
Overnight tornado watches and warnings were announced in several parts of Arkansas, Tennessee and Mississippi. (Additional reporting by Brendan O'Brien in Milwaukee and Kevin Murphy in Kansas City, Missouri; Writing by Dan Whitcomb, Brendan O'Brien and Chris Michaud; Editing by Simon Cameron-Moore and Paul Tait)