AKIPRESS.COM - More than 300 people were missing after a ferry sank off South Korea, the coastguard said on Wednesday, with a three-fold increase in the number of passengers unaccounted for put down to a miscalculation by officials.

The ferry was carrying 477 people, of whom 164 were confirmed rescued, coastguard officials said. Two people were confirmed dead after the ferry listed heavily onto its side and capsized in apparently calm conditions off South Korea's southwest coast.

The Ministry of Security and Public Administration had reported that 368 people had been rescued and that about 100 were missing.

It later described those figures as a miscalculation, turning what had first appeared to be a largely successful rescue operation into potentially a major disaster.

The cause of the disaster was not immediately clear, Reuters said.

Most of those on board were children and their teachers from a high school in Seoul on a field trip to Jeju island, about 100 km (60 miles) south of the Korean peninsula.

There were 477 people and 150 vehicles on board the ferry Sewol, officials said. Witnesses said many people were likely still inside the stricken vessel.