South Korea's daily new coronavirus cases stayed in the 600s for the second straight day Thursday on sporadic cluster infections amid concerns over virus variants. 

The country reported 610 new cases, including 576 local infections, raising the total caseload to 153,155, the Korea Disease Control and Prevention Agency (KDCA) said.

Cluster infections involving churches, restaurants, gymnasiums and hospitals continue to take place across the country, and virus variant cases stayed at 30 to 40 in the past week.  

The country added one COVID-19 death, raising the death toll to 2,008. The fatality rate came to 1.31 percent.

The number of daily imported cases fell to 34 after exceeding 40 in the past four days, raising worries of the potential transmission of coronavirus variants, especially the more transmissible Delta variant first detected in India.  

South Korea has yet to report a large number of Delta variant cases, but other countries, such as Britain and the United States, whose vaccination rates topped 50 percent, have been struggling with rising cases of the variant.

The woes over variant cases came as South Korea is set to ease its social distancing scheme in July amid its vaccination drive, which allows businesses to stay open longer and permits gatherings of more people.

Currently, the greater Seoul area is under Level 2 distancing in the five-level scheme, while the rest of the country is under Level 1.5. Private gatherings of five or more are banned nationwide.

Under the new four-tier system, restaurants and cafes in the capital area will be permitted to operate until midnight under Level 2, an extension from the current restrictions of 10 p.m.

The nationwide ban on gatherings of five or more people will be lifted under the renewed guidelines, with the ceiling set to be raised to eight under Level 2. No restrictions are applied under Level 1.

In the greater Seoul area, the ceiling will initially be set at six people for the first two weeks of next month.

The upsurge in the daily caseload came as the country's vaccination drive has been gaining traction.

A total of 15.15 million people, or 29.5 percent of the country's 51.3 million population, have received their first shots of COVID-19 vaccines since the vaccine rollout in late February. Of them, 4.4 million, or 8.6 percent of the population, were fully inoculated as of Thursday.

The country aims to inoculate 36 million with at least one jab by September to achieve herd immunity in November.

Of the newly confirmed locally transmitted cases, 251 came from Seoul and 184 from Gyeonggi Province that surrounds the capital.

The southern port city of Busan added 16 cases. Daejeon, 160 kilometers south of Seoul, added 15 cases, and Incheon, just west of Seoul, added 15 patients. The southeastern port city of Ulsan had 11 more cases.

Health authorities counted 34 more imported cases, raising the tally to 9,685.

Of the imported cases, Asian countries, excluding China, accounted for 30, followed by the United States with three cases and Europe with one case.

The number of patients in serious or critical condition came to 141, down five from the previous day.

The total number of people released from quarantine after making full recoveries was 144,788, up 409 from a day earlier.

South Korea has carried out 10.44 million COVID-19 tests, including 28,833 the previous day. (Yonhap)