South Korea's daily new coronavirus cases stayed in the 400s for the third day in a row on Saturday, as health authorities scrambled to contain cluster infections linked to mission schools nationwide.

The country added 458 more COVID-19 cases, including 423 locally transmitted infections, raising the total caseload to 77,850, according to the Korea Disease Control and Prevention Agency.

The figure was down from 469 on Friday and compared with 497 on Thursday and 559 on Wednesday.

The country added 15 more deaths, raising the total to 1,414. The number of patients with serious symptoms across the country reached 231.

Due to a continued rise in cluster infections from religious facilities, health authorities delayed their decision on whether to extend or ease the current social distancing measures to Sunday.

Health authorities are expected to decide the level of social distancing measures over the weekend, but they appear to be very cautious in sharply lowering the level ahead of the Lunar New Year holiday slated for Feb. 11-13.

Clusters of infections originating from religious, medical and nursing facilities have been spreading across the country.

The number of infected people tied to six unauthorized education facilities run by a local Christian missionary group called the International Mission rose to 355 as of Friday night, up 15 from Thursday.

Seoul's Hanyang University Hospital has reported at least 23 confirmed cases, while clusters from a central Seoul welfare facility and a southern Seoul workplace have reported 35 and 44 patients, respectively.

Jeon Hae-cheol, minister of the interior and safety, told reporters that there are worries that the coronavirus could further spread because of cluster infections at the IM missionary society.

"Given growing uncertainties over a recent COVID-19 situation, the government is cautiously reviewing a change of social distancing rules," Jeon said.

Level 2.5, the second highest in the country's five-tier scheme, has been applied in the greater Seoul area since early December, with Level 2 in other areas. Bans on gatherings of five or more people have been in place across almost the entire country.

Lim Sook-young, a senior official of the KDCA, told reporters that the reproduction rate of the new coronavirus here recently rose above 1. The rate measures the number of people that the average patient infects.

When the reproduction rate is above 1, it means that the outbreak is spreading. When the rate is below 1, it means that the outbreak is shrinking. 

Lim said the data could be an early sign that the number of new infections is growing, but health authorities are closely monitoring the situation to determine whether the indicator is tentative.

Of the additional locally transmitted cases, 152 came from Seoul and 136 were reported from Gyeonggi Province that surrounds the capital. Incheon, 40 km west of Seoul, reported 15 more cases. The three areas account for around half of the nation's population.

The total number of people released from quarantine after making full recoveries moved up 618 to 67,121. (Yonhap)