South Korea on Friday reported 29 more coronavirus cases, with most tied to cluster infections in Seoul, putting health authorities on alert against secondary and tertiary infections.

The 27 new cases of COVID-19 detected Thursday, with 22 of them being local infections, brought the nation's total number to 11,018, according to the Korea Centers for Disease Control and Prevention.

The number of cases connected to bars and clubs in Seoul's popular nightlife district of Itaewon has reached at least 142 as of late Thursday, according to the KCDC and the Seoul city government.

Health authorities are staying vigilant against the community spread of COVID-19 connected to the Itaewon cluster that began early this month, urging those who visited places in the neighborhood to get virus tests.

They view this weekend as a critical juncture for the country to contain the further spread of the new coronavirus tied to the capital city's second-largest mass infection.

South Korea had added fewer than 15 cases of COVID-19 since mid-April, with the number of domestic infections even falling to zero on some days.

However, the number of daily new cases has been between 20 and 30 for the past week after the country saw an unexpected spike in cases coming from entertainment facilities in Seoul's Itaewon area, with secondary and tertiary infections reported not only in Seoul but across the country.

Of the 22 new local infections, 14 are from Seoul, followed by the western port city of Incheon with four, the KCDC said.

Imported cases, previously the biggest threat for South Korea's quarantine operations, are now less of a concern, though the country reported five more such cases Friday.

South Korea's virus deaths remained the same at 260, according to the KCDC, with the mortality rate reaching 2.37 percent.

The total number of people released from quarantine after full recoveries stood at 9,821, up 59 from a day earlier, the KCDC said.

The country has carried out COVID-19 tests on 726,747 people since Jan. 3, including 15,263 from a day earlier.

The number of people undergoing tests has spiked recently due to cases linked to nightspots in Itaewon. More than 35,000 people have been tested over the Itaewon infection cluster, according to the KCDC.

On May 6, the country switched to an "everyday life quarantine" and the normalization of public facilities and other business establishments, under the condition they follow basic sanitation measures.

However, due to the recent surge in virus cases traced to the Itaewon area, the country has decided to push back the reopening of schools by one week, allowing students to begin physically attending classes in phases Wednesday. (Yonhap)