Almost 300 people remain unaccounted for after a ferry carrying 459 people capsized and sank off South Korea.

The ferry, carrying mainly school students, was travelling from the port of Incheon, in the north-west, to the southern resort island of Jeju.

A major rescue effort is under way, involving dozens of ships and helicopters. Those brought to safety were taken to a nearby island.

Four people are now said to have died and dozens of others have been hurt.

South Korean officials had earlier said that 368 people had been plucked to safety, but later said there had been a counting error.

They have now revised down the number rescued to 164.

Images showed the ferry listing at a severe angle and then later almost completely submerged, with only a small part of its hull visible. It sank within two hours of sending a distress signal, reports said.

There are fears this could turn out to be South Korea’s biggest maritime disaster in almost 20 years, says the BBC’s Martin Patience in Seoul.

Several coast guard, military and commercial vessels were involved in the rescue effort, which unfolded rapidly on Wednesday morning.

Pictures from the scene showed rescue teams balanced on the sinking hull pulling teenagers from cabin windows. Some of their classmates jumped into the sea as the ship went down.

Reports suggest some of those rescued were picked up by nearby commercial vessels. The US Navy was also reported to be sending a ship to assist.

Navy divers were now searching the scene for those unaccounted for, officials said, but the work was challenging.

“There is so much mud in the sea water and the visibility is very low,” said Lee Gyeong-og, vice-minister of security and public administration.

One body, of a female crew member, had been recovered from the ship, the coastguard said. Another person, a male high school student, died after being rescued.

One student told local media her friends became trapped.

“Currently, I am in the middle of being rescued. At the time, the ship was turning on its side, and none of us were moving as we were told not to move as it was dangerous,” the unnamed student said.

“So, I am not well aware of the situation, but I am told that my friends and other friends could not escape as the passage was blocked. It seems that there are many students who could not get out as the passage was blocked by water.”

It is not yet clear what caused the incident, but witnesses described hearing an impact, before the ship listed and quickly sank.

•Credit: BBC. Photo shows rescue workers at work.