South Korea's daily new coronavirus cases stayed in the 500s for the third straight day Friday, as cluster infections continued to emerge across the nation. Social distancing rules were tightened in some cities, including Busan and Jeonju.

The country reported 558 more COVID-19 cases, including 533 local infections, raising the total caseload to 104,194, the Korea Disease Control and Prevention Agency (KDCA) said.

The country added two more deaths from COVID-19, increasing the total to 1,737.

In South Korea, a third wave of infections, which began in mid-November last year, has shown little signs of slowing down, with the nation reporting daily cases that have hovered around 400 over the past week.

Health authorities have warned of another wave as cluster infections have continued to emerge at various facilities, including saunas, religious gatherings and workplaces.

As of Thursday, the reproduction rate slightly fell to 1.36, which indicates that a single COVID-19 patient transmits the disease to more than one person. A day earlier, the rate was 1.39.

Over the past month, authorities found a total of 9,677 cases that violated social distancing protocols. Of them, fines were imposed on 2,396 cases, officials said.

Ahead of the Easter weekend and by-elections next week, health authorities have urged people to comply with distancing rules.

To contain the continued rise in new infections, health authorities extended the current Level 2 social distancing rules in the greater Seoul area, where more than half of the country's overall population resides, and Level 1.5 for the rest of the country for another two weeks until April 11.

Starting Friday, Busan, the nation's second-largest city, and Jeonju, 243 kilometers south of Seoul, will raise their social distancing rules to Level 2 amid a spike in cluster infections.

Bans on gatherings of five or more people will continue, and restaurants and other public facilities in the greater Seoul area are allowed to remain open till 10 p.m.

Since Feb. 26, when the country initiated its vaccination program, a total of 914,069 people have been given COVID-19 vaccine shots, including 36,125 people on Thursday.

AstraZeneca's vaccine took up 834,226, while Pfizer's accounted for 79,843, according to the KDCA.

A total of 10,821 cases of side effects after vaccinations have been reported, though 10,668 of them were mild symptoms.

A total of 30 deaths after vaccinations have been reported, according to the KDCA.

South Korea seeks to vaccinate 12 million people by June, and it aims to achieve herd immunity by November.

In the first half of the year, a total of 18.08 million doses of vaccines are scheduled to be delivered here, with around 2.69 million vaccine doses already shipped in as of March. During the April-June period, at least 15.39 million doses, which include 9.1 million AstraZeneca vaccines, are confirmed to be transported here, according to the KCDC.

The country is also making efforts to secure vaccines from other suppliers, including Janssen and Moderna.

The country began vaccination of citizens aged 75 and above starting Thursday. Authorities plan to provide jabs to those aged from 65 to 74 in May.

"While some countries are limiting application of AstraZeneca vaccine for certain age groups, South Korea plans to continue monitoring situations at home and abroad," KDCA Commissioner Jeong Eun-kyeong said.

Authorities plan to use low dead space (LDS) syringes designed to minimize wasted vaccine doses by reducing space between the needle and the plunger to maximize the number of recipients.

The country also plans to provide AstraZeneca vaccines with an inter-dose interval of around eight to 12 weeks.

So far, a total of 60 people were confirmed to have been infected after getting vaccinated, which translates into 8.3 cases for every 100,000 people. The findings were based on a study on 72,926 South Koreans who were inoculated from late February to March.

Of the patients, 56 received AstraZeneca's vaccine, while Pfizer's accounted for four.

Of the 533 locally transmitted cases, Seoul reported 165, and Gyeonggi Province that surrounds the capital city saw 156 new patients. Incheon, 40 kilometers west of Seoul, reported 22 more cases. The number of imported cases came to 25, up from 14 the previous day.

A university dormitory in Seoul reported nine new patients, raising the total caseload to 10. A bar in southern Seoul also identified 13 additional cases.

In Osan, 55 km south of Seoul, a day care center reported four new cases, with the total reaching 25 so far.

An elementary school in the central administrative city of Sejong found four new cases, raising the tally to 25.

The number of patients with serious symptoms across the country reached 101, down from 107 the previous day, the KDCA said.

The total number of people released from quarantine after making full recoveries moved up 422 to 95,861. (Yonhap)