South Korea dispatched coast guard and military rescue boats and helicopters to aid a passenger ferry carrying 476 people that's sinking off the nation's southwest coast.

The vessel is owned and operated by Chonghaejin Marine Co., a company official said by phone, asking not to be named citing internal policy. No passengers have been harmed so far in the incident, Mokpo coast guard official Park Jung Il said by phone. About 110 passengers of the 476 total have been rescued so far, Ministry of Security and Public Administration Vice Minister Lee Gyeong Og said in a televised briefing.

YTN TV footage showed the vessel, named "Sewol" or "time and tide" in Korean, mostly submerged on its side in calm waters near the shore off Jindo island, northwest of Jeju. The ship may have hit rocks in heavy fog, the broadcaster said, citing a South Korean government official.

A total of 324 students from Danwon High School southwest of Seoul were on board the ship, accompanied by 14 teachers, school official Kim Tae Eun said by phone. The students were on a school excursion to Jeju island, Kim said.

The 6,825-ton ferry can carry as many as 921 passengers and 130 vehicles.