An Asiana Airlines Boeing 777 passenger jet crashed and burst into flames as it landed short of the runway at San Francisco International Airport, killing two people and injuring 182 others.
Flight 214 originated in Shanghai, and had 307 people on board -- 291 passengers and 16 crew -- after it stopped to pick up passengers in Seoul. The aircraft apparently struck a rocky area at the water's edge short of the airport runway on Saturday.
"It is incredible and very lucky that we have so many survivors. But there are still many that are critically injured," said San Francisco Mayor Edwin Lee, who sent condolences to the families of those killed and hurt.
The crash sheared off the plane's landing gear and tore the tail off the fuselage.
San Francisco International Airport was immediately closed, though two runways later reopened. Some flights were diverted to Los Angeles.
Aboard the flight were 141 Chinese nationals, 77 South Koreans, 61 Americans, one Japanese, three Indians, three Canadians, one French, one Vietnamese, three others with unidentified nationality and 16 crew members, according to Asiana.
Anxious relatives swarmed the airline's headquarters in Seoul, seeking details of the crash and information on the victims.
The two people killed were Chinese passengers sitting in back seats, said Yoon Young-Doo, the CEO of the Seoul-based airline.
South Korea's transport ministry said separately they were both women, born in 1996 and 1997.
The ministry also said the plane's tail hit the runway and the aircraft veered to the left off the runway.
Yoon was remorseful as he spoke at a press conference in Seoul. "Please accept my deepest apology," the CEO said, bowing in front of TV cameras.
Yoon said his company bought the plane in 2006, and that "currently we understand that there are no engine or mechanical problems."
The plane was flown by experienced pilots, and there was no emergency warning ahead of the crash. "Our pilots strictly comply with aviation rules," Yoon said.
San Francisco General Hospital said it was treating 34 patients, five of them in critical condition. Other patients were rushed to different area hospitals.
In total, 123 people aboard the flight escaped unharmed, US officials said.
Survivor Elliott Stone told CNN that as it came in to land, it appeared the plane "sped up, like the pilot knew he was short."
"And then the back end just hit and flies up in the air and everybody's head goes up to the ceiling."
Video footage showed the jet on its belly surrounded by at least six fire engines that sprayed white foam on the wreckage. Debris was scattered on the runway and in the surrounding area.
A four-member South Korean government team was also heading to inspect the site of the accident, officials in Seoul said.
One dramatic photo tweeted by a survivor showed people streaming out of the jet following the crash-landing. 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 passenger, David Eun, wrote on Twitter.
But another photo from above showed a more distressing scene, with most of the roof of the plane missing and the cabin seating area charred by fire. The aircraft's wings were still attached.
"I saw some passengers bleeding and being loaded onto an ambulance," another passenger, Chun Ki-Wan, told YTN TV in Seoul.
"Everything seemed to be normal before it crash-landed."
Facebook Chief Operating Officer Sheryl Sandberg was supposed to be on the flight with her family and three colleagues, but switched to a United Airlines flight and arrived in San Francisco some 20 minutes before the Asiana crash.
"Serious moment to give thanks," she wrote on her own Facebook page.
The White House said President Barack Obama had been briefed on the incident, noting: "His thoughts and prayers go out to the families who lost a loved one and all those affected by the crash."
South Korean President Park Geun-Hye offered his "deepest condolences to the victims and their relatives," and promised that all government agencies concerned "will join forces to provide all necessary assistance and resources to deal with the disaster."
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.
It was the first fatal crash involving an Asiana passenger plane since June 1993, when a Boeing 737 operated by the carrier crashed into a mountain in South Korea, killing 68.
The US Federal Bureau of Investigation (FBI) said there was no indication that terrorism was to blame for the crash.
In Washington, National Transportation Safety Board experts flew west to investigate the crash, while the heads of the US Department of Transportation and the Federal Aviation Administration issued a joint statement thanking the first responders.
"Our thoughts and prayers go out to the passengers and crew of Asiana Flight 214 and their families," the statement read.