A ferry carrying 459 people, mostly high school students on an overnight trip to a tourist island, has sunk off South Korea's southern coast, leaving nearly 300 people missing.
At least four people were confirmed dead and 55 injured on Wednesday, according to the Associated Press, after an hours-long rescue effort by dozens of ships and helicopters.
The high number of people unaccounted for - perhaps trapped in the ship or floating in the ocean - raised fears that the death toll could rise drastically, making it one of South Korea's biggest ferry disasters since 1993, when 292 people died.
Al Jazeera's Harry Fawcett, reporting from Seoul, said: "As well as rescue workers, there are dozens of grief-stricken relatives, some of those now do believe their young loved ones are dead.
"We heard from one father saying that they should just raise the ship now. He said everybody that's trapped on that ship must be dead. He just wants to see the body of his 17-year-old son."
One student, Lim Hyung-min, told broadcaster YTN after being rescued that he and other students jumped into the ocean wearing life jackets and then swam to a nearby rescue boat.
"As the ferry was shaking and tilting, we all tripped and bumped into each another," Lim said, adding that some people were bleeding.
Once he jumped, the ocean "was so cold. I was hurrying, thinking that I wanted to live."
Local television stations broadcast live pictures of the ship, Sewol, listing to its side and slowly sinking as passengers jumped out or were winched up by helicopters.
At least 87 vessels and 18 aircraft swarmed around the stricken ship.
Rescuers clambered over its sides, pulling out passengers wearing orange life jackets.
But the ship overturned completely and continued to sink slowly.
Within a few hours only its blue-and-white bow stuck out of the water.
Very soon, that too disappeared.
The ship had set sail from Incheon, a city in South Korea's northwest and the site of the country's main international airport, on Tuesday night for an overnight, 14-hour journey to the tourist island of Jeju.
Three hours from its destination, the ferry sent a distress call at about 9am on Wednesday after it began listing to one side, according to the Ministry of Security and Public Administration.
Officials did not know what caused it to sink and said the focus was still on rescuing survivors.
Lee Gyeong-og, a vice minister for South Korea's Public Administration and Security Ministry, said 30 crew members, 325 high school students, 15 school teachers and 89 non-student passengers were aboard the ship.
Kang Byung-kyu, a government minister, said two of the dead were a female crew member and a male high school student. He said a third body was also believed to be that of a student.
A coast guard officer confirmed a fourth fatality but had no immediate details about it.
Kang said 164 people were rescued, of whom 55 were injured. Officials said 292 people were missing.