South Korea's daily new coronavirus cases spiked to a two-week high of over 600 on Wednesday as virus variants are emerging as another major challenge in the country's virus fight amid the accelerating vaccine rollout.

The country reported 645 new cases, including 605 local infections, raising the total caseload to 152,545, the Korea Disease Control and Prevention Agency (KDCA) said.

The country added one COVID-19 death, raising the death toll to 2,007. The fatality rate came to 1.32 percent.

The number of daily imported cases exceeded 40 for the fourth consecutive day amid woes over potential transmission of the coronavirus variants, especially the more transmissible Delta variant believed to have originated in India.

South Korea has yet to report a large number of the 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 the country is set to ease its social distancing scheme in July amid the 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 15.07 million people, or 29.4 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, 4.1 million, or 8.4 percent of the population, were fully inoculated as of Wednesday.

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

South Korea currently administers two-part vaccines from AstraZeneca, Pfizer and Moderna as well as Janssen's single-dose vaccine.

A total of 76,109 cases of side effects after vaccinations have been reported, although 95 percent of them were mild symptoms, such as a fever or muscle pain.

So far, 309 post-vaccination deaths have been reported, but health authorities acknowledged one case linked to vaccination.

Of the newly confirmed locally transmitted cases, 228 came from Seoul and 180 from Gyeonggi Province.

Daejeon, 160 kilometers south of Seoul, added 57 cases. Incheon, 40 km west of Seoul, added 26 patients, and the southeastern port city of Busan had 13 more cases.

Health authorities counted 40 more imported cases, raising the tally to 9,611.

Of the imported cases, Asian countries, excluding China, accounted for 29, followed by the United States with four cases, Europe with four, Africa with two and Columbia with one.

The number of patients in serious or critical condition came to 146, up 11 from the previous day.

The total number of people released from quarantine after making full recoveries was 144,379, up 562 from a day earlier.

South Korea has carried out 10.41 million COVID-19 tests so far, including 29,906 the previous day. (Yonhap)