Rescued passengers are escorted by members of a rescue team upon their arrival at a port in Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. More than 100 people were still unaccounted Wednesday several hours after a ferry carrying 476, most of them high school students, sank in cold waters off South Korea's southern coast, killing at least two and injuring 14, officials said. (AP Photo/Yonhap, Park Chul-heung) KOREA OUT

South Korean rescue helicopters fly over a South Korean passenger ship, trying to rescue passengers from the ship in water off the southern coast in South Korea, Wednesday, April 16, 2014. The South Korean passenger ship carrying more than 470 people, including many high school students, is sinking off the country's southern coast Wednesday after sending a distress call, officials said. There are no immediate reports of causalities. (AP Photo/Yonhap) KOREA OUT

In this photo released by Jeollanamdo via Yonhap News Agency, South Korean rescue team boats and fishing boats try to rescue passengers of a ferry sinking off South Korea's southern coast, in the water off the southern coast near Jindo, south of Seoul, Wednesday, April 16, 2014. Nearly 300 people were still missing Wednesday several hours after a ferry carrying 477, most of them high school students, sank in cold waters off South Korea's southern coast. (AP Photo/Jeollanamdo via Yonhap) KOREA OUT

Rescued passengers from a ferry sinking off South Korea's southern coast, are escorted by rescue teams on their arrival at a port in Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. More than 100 people were still unaccounted Wednesday several hours after the ferry carrying 476, most of them high school students, sank in cold waters off South Korea's southern coast. (AP Photo/Yonhap, Park Chul-heung) KOREA OUT

People watch a TV news program showing a sinking passenger ship, at Seoul Railway Station in Seoul, South Korea, Wednesday, April 16, 2014. The South Korean passenger ship carrying more than 470 people, including many high school students, is sinking off the country's southern coast Wednesday after sending a distress call, officials said. There are no immediate reports of causalities.(AP Photo/Ahn Young-joon)

This undated photo shows South Korean passenger ship Sewol. A government office said Wednesday, April 16, 2014 the South Korean passenger ship carrying about 470 people have sent a distress call off the southern coast after it began tittering to one side. (AP Photo/Yonhap) KOREA OUT

South Korean coast guard officers try to rescue passengers from ferry Sewol in the water off the southern coast near Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. Dozens of boats, helicopters and divers scrambled Wednesday to rescue more than 470 people, including 325 high school students on a school trip, after the ferry sank off South Korea's southern coast. (AP Photo/Hyung Min-woo, Yonhap) KOREA OUT

South Korean coast guard officers try to rescue passengers from ferry Sewol in the water off the southern coast near Jindo, south of Seoul, South Korea, Wednesday, April 16, 2014. Dozens of boats, helicopters and divers scrambled Wednesday to rescue more than 470 people, including 325 high school students on a school trip, after the ferry sank off South Korea's southern coast. (AP Photo/Hyung Min-woo, Yonhap) KOREA OUT

In this image taken from video from Mokpo Coast Guard, passengers from a ferry sinking off South Korea's southern coast, are rescued by South Korean Coast guard in the water off the southern coast near Jindo, south of Seoul, Wednesday, April 16, 2014. Nearly 300 people were still missing Wednesday several hours after the ferry carrying 477, most of them high school students, sank in cold waters off South Korea's southern coast. (AP Photo/Yonhap) KOREA OUT

JINDO-GUN, SOUTH KOREA - APRIL 16: In this handout image provided by the Republic of Korea Coast Guard, passengers are rescued by the Republic of Korea Coast Guard from a ferry sinking off the coast of Jindo Island on April 16, 2014 in Jindo-gun, South Korea. The ferry identified as the Sewol was carrying about 470 passengers, including students and teachers, traveling to Jeju island. (Photo by The Republic of Korea Coast Guard via Getty Images)

JINDO-GUN, SOUTH KOREA - APRIL 16: In this screen shot handout of helicopter camera provided by the Republic of Korea Coat Guard, the ferry is seen sinking off as the rescue work continues the coast of Jindo Island on April 16, 2014 in Jindo-gun, South Korea. Two people are dead, and more than ninety are missing as reported. The ferry identified as the Sewol was carrying about 470 passengers, including the students and teachers, traveling to Jeju island. (Photo by The Republic of Korea Coast Guard via Getty Images)

JINDO-GUN, SOUTH KOREA - APRIL 16: In this handout image provided by the South Korean Navy, the ferry is seen sinking as the rescue work continues off the coast of Jindo Island on April 16, 2014 in Jindo-gun, South Korea. Two people are dead, and more than ninety are missing as reported. The ferry identified as the Sewol was carrying about 470 passengers, including the students and teachers, traveling to Jeju island. (Photo by The South Korean Navy via Getty Images)

JINDO-GUN, SOUTH KOREA - APRIL 16: In this screen shot handout of helicopter camera provided by the Republic of Korea Coat Guard, the ferry is seen sinking as the rescue work continues off the coast of Jindo Island on April 16, 2014 in Jindo-gun, South Korea. Two people are dead, and more than ninety are missing as reported. The ferry identified as the Sewol was carrying about 470 passengers, including the students and teachers, traveling to Jeju island. (Photo by The Republic of Korea Coast Guard via Getty Images)

One passenger rescued from the Korean ferry said he believed many people were trapped inside the vessel when it sank. The ferry is pictured above as the rescue work continues off the coast of Jindo Island on April 16, 2014 in Jindo-gun, South Korea.

The US navy has joined a massive rescue operation in the search for hundreds of passengers, many of them school pupils, who are missing after a ferry carrying 476 people, capsized off the South Korean coast. The vessel had been travelling to the southern island of Jeju

The Sewol ferry, which had been carrying students from the Danwon high school in Ansan city near Seoul, had been travelling from the north-western port of Incheon to the popular southern tourist island of Jeju for a four day trip when it capsized.Authorities confirmed three people had died and 297 were unaccounted for.

The US Seventh Fleet said the amphibious assault ship USS Bonhomme Richard, which has helicopters on board, was on a routine patrol off South Korea's west coast and was on its way to the scene of the accident.

One rescued passenger said he believed many people were trapped inside the ferry when it sank.

More than 30 navy and coastguard divers are searching the near-sunken ship for survivors, according to emergency officials.

The vessel sent a distress call after it began listing, according to the Ministry of Security and Public Administration. The government said about 95% of the ferry, whose passengers included 325 high school students on a trip to the popular tourist island, was submerged.

Lee Gyeong-og, a vice-minister in charge of the central government's emergency response team, said that the actual number of people rescued could be higher, since many passengers had been picked up by fishing boats and taken to different ports on the islands scattered in the region.

But the national news agency Yonhap quoted one rescued passenger as saying that people in the ferry's cafeteria and games room below the main passenger decks might not have escaped.

"The internal broadcast advised us to remain in our seats," Yonhap quoted the 57-year-old passenger, which it identified only by his last name, Yoo, as saying. "But I could not stay put because the water was coming up. So I came outside with my life jacket on."

"I wonder why they didn't tell us to evacuate immediately," he added.

Media photos showed wet students, some without shoes, some wrapped in blankets, tended to by emergency workers. One student, Lim Hyung-min, told broadcaster YTN from a gym on a nearby island 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," Mr 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," he said.

The water temperature in the area was cold enough to cause signs of hypothermia after about 90 minutes or two hours, according to an emergency official. Mud on the ocean floor made underwater search operations difficult.

One rescued passenger said he believed many people were trapped inside the ferry when it sank.

More than 30 navy and coastguard divers are searching the near-sunken ship for survivors, according to emergency officials.

The vessel sent a distress call after it began listing, according to the Ministry of Security and Public Administration. The government said about 95% of the ferry, whose passengers included 325 high school students on a trip to the popular tourist island, was submerged.

Two coastguard officers said a 27-year-old woman named Park Ji-yeong and another unidentified person had died. The government said five hours after the distress call that 368 of the 476 passengers had been rescued, but officials gave no further details, including what caused the ferry to sink or the conditions of the other passengers.

Photos showed wet students wrapped in blankets as emergency workers tended to them.

One student, Lim Hyung-min, told broadcaster YTN from a gym on a nearby island that he jumped into the ocean wearing a life jacket with other students 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".

The water temperature in the area was about 12C, cold enough to cause signs of hypothermia after about 90 minutes, according to an emergency official.

Local media ran photos showing the partially submerged ferry listing dramatically as helicopters flew overhead and rescue vessels and a small boat covered with an orange tarpaulin floated nearby.

Passenger Kim Seong-mok, speaking from a nearby island after his rescue, told YTN he was "certain" that many people were trapped inside the ship as water quickly filled up inside and the severe tilt of the ferry kept them from reaching the exits.

Some people yelled at those who could not get out, urging them to break windows.

Kim said that after having breakfast he felt the ferry tilt and then heard it crash into something. He said the ferry operator made an announcement asking that passengers wait and not move from their places. Kim said he did not hear any announcement telling passengers to escape.

The students are from a high school in Ansan city near Seoul, and were on their way to Jeju island for a four-day trip, according to a relief team set up by Gyeonggi province, which governs the city. The ferry left Incheon port, just west of Seoul, on Tuesday evening, according to the state-run Busan Regional Maritime Affairs & Port Administration.

At the high school, students were sent home and parents gathered for news about the ferry.

Park Ji-hee, a first-year student, said she saw about a dozen parents crying at the school entrance and many cars and taxis gathered at the gate as she left in the morning.

She said some students in her classroom began to cry as they saw the news on their mobile phones. Teachers tried to soothe them, saying the students on the ferry would be fine.

A total of 16 helicopters, 34 rescue vessels and navy divers were sent to the area, Lee Gyeong-og, a vice minister for South Korea's Public Administration and Security Ministry, told a televised news conference.

He said 14 had been injured so far, including one described as serious, and taken to hospital.

Belfast Telegraph