South Korea's daily new coronavirus cases surpassed 500 for the fourth day in a row on Saturday, ringing an alarm bell over a possible resurgence across the nation in the midst of the spring season.

The country reported 543 more COVID-19 cases, including 521 local infections, raising the total caseload to 104,736, the Korea Disease Control and Prevention Agency (KDCA) said.

The country added three more deaths from COVID-19, increasing the total to 1,740.

The daily number has stayed over 500 since Wednesday, when the number jumped by nearly 60 to a 40-day high of 506.

Health authorities said virus infections are accelerating across the country as the movement of people increases amid spring weather.

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

Authorities have urged people to comply with distancing rules over the Easter weekend and by-elections next week.

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

The rest of the county will be put under Level 1.5 for the same period.

However, the two cities of Busan, the nation's second-largest city, and Jeonju, 243 kilometers south of Seoul, toughened social distancing to Level 2 starting from Friday amid a spike in cluster infections.

Under Level 2, gatherings of five or more people are banned, while restaurants and other public facilities are allowed to remain open till 10 p.m.

Since the country initiated its vaccination program on Feb. 26, a total of 914,069 people have been given COVID-19 vaccine shots, including 36,125 people on Friday. The total accounts for 1.75 percent of the country's population of 52 million.

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.

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

Of the 521 locally transmitted cases, Seoul reported 154, and Gyeonggi Province that surrounds the capital city saw 143 new patients. The southern port city of Busan reported 61 more cases.

The number of imported cases came to 22, down from 25 the previous day.

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

The total number of people released from quarantine after making full recoveries moved up 335 to 96,196. (Yonhap)