The three new cases in the outbreak of Middle East Respiratory Syndrome, including two medical workers, put the total number of those infected at 169, the health ministry said.
The number of deaths remained unchanged at 25.
The two medical staff include a doctor who treated a MERS patient at Samsung Medical Centre in Seoul, seen as the epicentre of the outbreak where more than 80 were infected.
Another was a medical worker who took X-rays of a MERS patient in another hospital in Seoul.
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The latest numbers came a day after South Korea reported no new cases, raising guarded hope that Seoul was winning the battle to contain the virus.
The number of new patients had been falling for three straight days from eight on Tuesday to none on Saturday.
The number of people exposed to patients and quarantined at state facilities or at home also fell to 4,035 yesterday from a height of more than 6,700 on Wednesday.