WASHINGTON - US rescue teams launched a massive hunt for survivors Tuesday after a tornado tore through a suburb of Oklahoma City, causing chaos and leaving dozens dead, including children.
State medical examiner's office spokeswoman Amy Elliott said 24 victims had been confirmed dead. Earlier reports had cited higher tolls, and the number is expected to rise as recovery efforts continue.
At least 101 people have been pulled alive from under debris, said Terri Watkins, spokeswoman for the Oklahoma Department of Emergency Management, and local broadcasters said more than 200 people have been injured.
Some of those killed by the mid-afternoon twister were children under 12, killed when the two-mile wide funnel of wind demolished an elementary school in the Oklahoma City suburb of Moore.
US President Barack Obama declared a "major disaster" as crews combed the wreckage of the shattered community, where even residents with long memories of past twisters were shocked by the devastation.
The killer system - packing powerful winds of up to 322 kilometres per hour - flattened block after block of homes, set off fires, downing power lines and tossed cars.
Stunned weather forecasters described an epic three-kilometre wide mid-afternoon storm, as news helicopter footage showed a dark twister plowing through densely packed suburbs.
"To me, this is this is bigger than anything I've ever seen. It's absolutely huge. It's horrific," Oklahoma Governor Mary Fallin told NBC's Today Show early Tuesday.
"It looked like somebody just set off something that just destroyed structures, not blocks, but miles of areas, and major buildings from hospitals to schools to banks to shopping centers, movie theaters."
Local television footage on Monday showed children as young as nine being pulled out of the Plaza Towers Elementary School in Moore, a residential community of 55,000 just south of Oklahoma's state capital.
"I had to hold onto the wall to keep myself safe," one little girl said.
The Moore Medical Center was evacuated after it sustained damage, and state authorities called out the National Guard to help rescue efforts as Obama ordered federal aid to supplement local recovery efforts.
The president was to be briefed on the disaster by top officials before delivering a statement at the White House at 10:00am (1400 GMT).
Rescue operations already hindered by the mounds of debris and fallen power lines could encounter further obstacles as the forecast calls for another bout of severe weather in the region.
On Twitter, the National Weather Service gave the tornado a preliminary rating of EF-4, indicating that it packed winds of 166 to 200 miles per hour - more severe than a category five hurricane.
In downtown Oklahoma City, tornado sirens went off at least three times and the Interstate 35 highway - a busy north-south artery through the American heartland - was closed to all but emergency vehicles.
In Moore, live images from KFOR television showed people wandering among the debris and even a couple of un-tethered horses from a local stable that managed to survive the punishing storm.
"I had no idea it was coming," said a stable worker, who told how he survived the "unbearably loud" twister by taking cover in one of the stalls.
Monday's tornado followed roughly the same track as a May 1999 twister that killed 44 people, injured hundreds more and destroyed thousands of homes.
Tornadoes frequently touch down on Oklahoma's wide open plains, but Monday's twister struck a populated urban area and raised fears of a high casualty toll.
Because of the hard ground, few homes are built with basements or storm shelters in which residents can take cover.
Oklahoma City lies inside the so-called "Tornado Alley" stretching from South Dakota to central Texas, an area particularly vulnerable to tornadoes.
But Moore's residents were shocked at the sprawling moon-like landscape left behind by the massive twister.
"There's nothing left of my house," an unidentified woman told CNN. "We've lost animals. We've lost everything."
Some 29,000 people remained without power early Tuesday, according to OG&E, the local utility.
In a sign that more chaos may be to come, the National Weather Service forecast the development of more tornadoes later Tuesday, with parts of Oklahoma, Arkansas, Louisiana and Texas most likely to be affected.