The health ministry said that all of the MERS cases had been linked to a 68-year-old man who returned home in early May from the Middle East, where MERS is not uncommon.
"We are making our utmost efforts to prevent the further spread of the disease," South Korean Health Minister Moon Hyung-pyo said, apologizing for failing to halt an outbreak of the MERS virus.
He added that the hospital where the first outbreak was registered had already been closed and that all patients were being treated in quarantine.
MERS is believed to be a respiratory illness, which is caused by a new type of corona-virus.
SARS has killed almost 800 people since the beginning of an outbreak in 2002.
According to the World Health Organization, a total of 1,139 MERS cases have been registered across the world, with the death toll currently standing at 431.
