South Korea's daily new coronavirus cases rose to more than 500 for the second day Thursday, with tightened social distancing rules to be implemented in the second-largest city of Busan over the continued emergence of cluster infections.

The country reported 551 more COVID-19 cases, including 537 local infections, raising the total caseload to 103,639, the Korea Disease Control and Prevention Agency (KDCA) said. It marked the highest daily tally in 41 days.

The country added four more deaths from COVID-19, increasing the total to 1,735.

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.

Cluster infections have continued to emerge at various facilities, including saunas, religious gatherings and workplaces.

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.

Yoon Tae-ho, a senior health official, told reporters that Busan will raise its social distancing rules to Level 2 from Friday. Some cities and provinces were also considering raising social distancing rules, Yoon said.

Health authorities have expressed concerns about a rise in COVID-19 infections outside the greater Seoul area.

Busan, the largest port city here, has reported more than 100 virus cases in the past week tied to bars and other facilities.

The KDCA said it will hold a meeting with experts on Friday to discuss the potential use of COVID-19 self-test kits.

The test kits for home use could be necessary as no end to the pandemic is in sight and another wave of coronavirus infections is possible, the KDCA said. 

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 876,573 people have been given COVID-19 vaccine shots, including 22,643 people on Wednesday.

AstraZeneca's vaccine took up 815,769, while Pfizer's accounted for 60,804, according to the KDCA.

A total of 10,698 cases of side effects after vaccinations have been reported, though 10,549 of them were mild symptoms.

A total of 28 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.

AstraZeneca COVID-19 shots for citizens aged 65 and older began earlier last week, and Pfizer vaccines are to be administered to people aged 75 and older starting Thursday.

Of the total 537 locally transmitted cases, Seoul reported 197, and Gyeonggi Province that surrounds the capital city saw 125 new patients. Incheon, 40 kilometers west of Seoul, reported 20 more cases. The number of imported cases came to 14, down from 15 the previous day.

Cases tied to a hospital in Seoul's Dobong Ward rose by 11 to 12. Cases involving an entertainment facility in Busan were up 20 to 136, and cases related to an elementary school in the administrative capital of Sejong were up 10 to 21.

The number of patients with serious symptoms across the country reached 107, down from 108 the previous day, the KDCA said.

The total number of people released from quarantine after making full recoveries moved up 409 to 95,439. (Yonhap)