An Asiana Airlines Boeing 777 aircraft crashed as it tried to land at San Francisco International Airport on Saturday, with its tail breaking off and smoke billowing out before the cabin eventually burned out.
There was no immediate confirmation of fatalities among about 300 people on the plane -- Flight 214 from Seoul -- and one apparent survivor tweeted a picture of passengers fleeing the jet.
Video footage showed the jet on its belly surrounded by firefighters and debris scattered on the runway and surrounding area.
There was no official explanation for the crash landing but footage appeared to show the tail struck the seawall at the edge of the runway.
Later footage showed the fuselage without the tail and at least part of the plane's landing gear was strewn across the runway and surrounding area.
US Federal Aviation Administration spokesman Lynn Lunsfor confirmed the crash landing and told AFP the airport has been closed until further notice. Some flights have been diverted to Los Angeles.
The National Transportation Safety Board (NTSB) has dispatched personnel to San Francisco to investigate the crash landing and a press conference was scheduled for 2130 GMT.
One dramatic photo tweeted by someone claiming to be a survivor showed people streaming out of the jet. An inflatable slide was at the front entrance. Other emergency exits also appeared to have been used.
"I just crash landed at SFO. Tail ripped off. Most everyone seems fine. I'm ok," the survivor, David Eun, wrote.
But another photo from above showed a more distressing scene, with almost the entire roof of the plane and the cabin seating area destroyed by fire. The aircraft's wings were still attached.
One passenger, Chun Ki-Wan, told YTN TV in Seoul by phone: "Most of the passengers escaped unhurt, following directions from the crew.
"I saw some passengers bleeding and being loaded onto an ambulance," Chun said.
"Everything seemed to be normal before it crash-landed."
Survivors have been ushered into a room at the airport guarded by police and airline personnel. Relatives were asked to wait a short distance away.
The plane left the South Korean capital on Friday and there were 292 passengers aboard, a spokesman for the airline confirmed, adding he did not know the specific number of crew on board.
The spokesman told AFP: "We understand it has crash-landed at a San Francisco airport. (...) We're still checking what has caused the accident and how many casualties have occurred."
Local media reported that at least 12 people were injured and cited multiple witnesses who said the plane had approached the runway at an awkward angle, with several onlookers saying they heard a loud bang.
Emergency crews were reporting passengers in need of burn treatment, according to Redwood City Fire Department.
Anthony Castorani, who saw the flight land from a nearby hotel, said he saw the plane touch the ground -- and then noticed a larger plume of white smoke.
"You heard a pop and you immediately saw a large, brief fireball that came from underneath the aircraft," he told CNN.
The accident site was covered in white foam used by firefighters, with at least six fire trucks at the scene.
California highway police temporarily closed all roads near the facility -- a major international hub, especially for flights to and from Asia.
Asiana Airlines is based in Seoul. The twin-engine 777 aircraft is one of the world's most popular long-distance planes, often used for flights of 12 hours or more, from one continent to another.