South Korea on Thursday reported 29 more coronavirus cases following cluster infections linked to clubs and bars in Seoul, putting health authorities on edge amid growing concerns over further virus spread.

The new cases of COVID-19, with 26 of them being local infections, brought the nation's total number to 10,991, according to the Korea Centers for Disease Control and Prevention (KCDC).

The number of cases connected to bars and clubs in Seoul's popular nightlife district of Itaewon reached 131 as of Thursday, according to the KCDC and the Seoul city government.

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.

But the number of daily new cases has hovered around 30 for the past three days after the country saw an unexpected spike in cases coming from entertainment facilities, with secondary and tertiary infections reported not only in Seoul but across the country.

Of the total 29 cases, 12 came from Incheon, west of Seoul, six from Gyeonggi Province, surrounding the capital city, and three each from Seoul and North Chungcheong Province, the KCDC said.

The KCDC said it has confirmed tertiary infections in Incheon after a private academy instructor lied about his occupation after his recent visit to a Itaewon club. So far, 11 confirmed virus cases are tied to him.

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

South Korea's virus death toll climbed to 260 after adding one more fatality, 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 9,762, up 67 from a day earlier, the KCDC said.  The country has carried out COVID-19 tests on 711,484 people since Jan. 3, including 15,564 from a day earlier.

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

"A total of some 15,000 tests were conducted yesterday alone with a total of 35,000 tests undergoing in connection with Itaewon clubs," Yoon Tae-ho, a senior health ministry official, said in a briefing.

Health authorities urged people to voluntarily get tested as those who do not follow the advice will face a fine of up to 2 million won ($1,600).

They also said 131 people who have violated self-isolation measures will be handed over to the prosecution. 

After flattening the curve of COVID-19, South Korea shifted last Wednesday to an "everyday life quarantine" scheme and the normalization of public facilities and other business establishments, under the condition they follow basic sanitation measures.

But 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 physically attend classes in phases starting next Wednesday.

Seoul and other municipal governments have issued an administrative order banning gatherings at entertainment establishments, which has de facto forced club and bar owners to suspend business. (Yonhap)