Health officials wearing protective suits talk at a coronavirus testing site in Seoul, Monday, March 22. AP

South Korea's daily new coronavirus cases bounced back to over 400 Wednesday as sporadic cluster infections continued at workplaces and private gatherings, spurring concerns over a resurgence in cases.

The country reported 428 more COVID-19 cases, including 411 local infections, raising the total caseload to 99,846, according to the Korea Disease Control and Prevention Agency (KDCA).

The country added three more deaths from COVID-19, increasing the total to 1,707. The fatality rate was 1.71 percent, the KDCA said.

Daily infections rebounded after falling to 346 on Tuesday. The daily caseload stayed above 400 for the previous six days through Monday.

To curb the pandemic in the greater Seoul area, which is home to roughly half of the country's 52 million population, the KDCA extended virus curbs, the third highest in the five-tier virus restriction that were set to expire on March 14 for another two weeks until March 28.

Health authorities said they will decide Friday whether to again extend the current virus curbs by another two weeks but given the current situation, the measures are highly likely to be extended.

The greater Seoul area has been under the Level 2 social distancing measures since February. The measures include attendance caps at schools, religious activities and sports events.

The country's COVID-19 vaccine rollout increased at a snail's pace as the AstraZeneca COVID-19 shot for elderly citizens aged 65 and older started on Tuesday. Health authorities assessed that there is no evidence suggesting a correlation between the vaccines and blood clots found in some recipients.

Earlier, the country started administering the second Pfizer shots on Saturday.

Pfizer vaccines for some 250,000 people arrived here on Wednesday for the inoculation of people aged 75 or older. The vaccines are part of Pfizer vaccines for 13 million people which will be provided under a deal with the U.S. pharmaceutical firm.

Under the country's vaccination program that started Feb. 26, the country seeks to vaccinate a total of 12 million people by June. Foreigners also will be inoculated under the program.

The country aims to achieve herd immunity by November.

Of the new locally transmitted cases, 135 came from Seoul and 150 were reported from Gyeonggi Province that surrounds the capital. Incheon, 40 kilometers west of Seoul, reported 21 more cases.

The number of imported cases came to 17, up from 15 the previous day. Cases from Asian countries, except for China, stood at seven, with cases from the United States, Europe and Africa at six, two, and two, respectively.

The number of seriously or critically ill COVID-19 patients was 111, up 10 from the previous day.

The total number of people released from quarantine after making full recoveries was 91,560, up 481 from a day earlier.

South Korea has carried out 7,441,210 COVID-19 tests, including 40,220 the previous day. (Yonhap)