South Korea's daily new virus cases bounced back to over 600 Wednesday due to sporadic cluster infections as the country's inoculation drive gains traction on increased vaccine supply.

The country reported 602 more COVID-19 cases, including 581 local infections, raising the total caseload to 145,692, the Korea Disease Control and Prevention Agency (KDCA) said.

Wednesday's figure was sharply up from 454 cases Tuesday. Daily cases here usually spike from Wednesday as more people get tested.

Daily caseloads have been going through some ups and downs between the 400s and 700s in recent months with no significant signs of a letup due to lingering cluster infections nationwide.

The country added two more deaths, raising the death toll to 1,977. The fatality rate was 1.36 percent.

A total of 9.2 million people, including 714,384 the previous day, have received their first shots of COVID-19 vaccines, accounting for 17.9 percent of the country's population since the country started its vaccination program on Feb. 26.

The KDCA said 2.32 million people, or 4.5 percent of the population, have been fully vaccinated with their second jabs.

Health authorities are speeding up vaccinations in order to inoculate 14 million people by the end of this month and 36 million by September. The country aims to achieve herd immunity in November but hopes it can be reached earlier than expected with the increased vaccine rollout.

Earlier Wednesday, the Pfizer vaccine for 325,000 people arrived in the country. Additional Pfizer vaccine doses for 975,000 people are scheduled to be supplied later this month.

The country began inoculating seniors aged 60-64 and military soldiers under age 30 from Monday. Reserve forces, civil defense members and others in charge of defense and foreign affairs are set to receive Johnson & Johnson's Janssen vaccine starting Thursday.

Health authorities said the Moderna vaccine can be administered starting next week.

A total of 38,242 cases have been reported, although 94.8 percent of them were mild symptoms.

So far, a total of 222 post-vaccination deaths have been reported, with 14 coming in the past two days, but the exact causes of the deaths remain unknown as causality could not be determined, health authorities said.

The government is looking to offer more incentives to vaccinated people to boost its inoculation campaign. It plans to allow overseas group tours of fully vaccinated citizens to countries with stable antivirus conditions as early as in July.

South Korea has been working to ink agreements that allow quarantine-free air travel with countries including Singapore, Taiwan and Guam.

Of the 581 newly locally transmitted cases, 181 came from Seoul, 155 from Gyeonggi Province and 21 from Incheon, 40 kilometers west of the capital.

The southeastern city of Daegu, once the country's virus hotspot, reported 44 more cases.

The number of cases traced to a bar in Daegu rose by 31 to 361. A restaurant for foreign workers in Changnyeong, South Gyeongsang Province, added 16 cases, raising its total to 68.

A karaoke facility in Cheongju, around 140 kilometers south of Seoul, reported eight more cases, bringing its total to 42.

There were 21 additional imported cases, up two from a day earlier, raising the total to 9,220.

Of the newly confirmed cases from overseas, four came from the United States and another four from Indonesia.

Health authorities are especially keeping close tabs on COVID-19 variants from overseas that are believed to be more contagious.

The KDCA data showed the number of seriously or critically ill COVID-19 patients was 146, down three from the previous day.

The total number of people released from quarantine after making full recoveries was 136,174, up 762 from a day earlier, with 7,541 people being isolated for COVID-19 treatment, down 162 from a day ago. (Yonhap)