
Yonhap news agency cited Coast Guard officials saying that about 130 people had already been taken off the ferry. The ship had listed to one side and was taking on water about 20 kilometres from the coast.
The passengers were mostly secondary school students on a field trip to Jeju island when the vessel sent a distress signal at about 9 am, it said.
President Park Geun-hye ordered all available vessels be mobilized in the rescue effort to prevent any loss of life.
DPA