South Korea's daily new coronavirus cases fell back to below 600 on Friday, while authorities are stepping up monitoring of manufacturing plants and hospitals to slow the rapid pace of virus transmission.

The country reported 561 more COVID-19 cases, including 533 local infections, raising the total caseload to 86,128, the Korea Disease Control and Prevention Agency (KDCA) said.

The country added six more deaths, raising the total to 1,550.

Friday's caseload was down from the previous two days when new cases stayed at the more than one-month high of over 600. The figure remained in the 300s from Saturday to Monday due mainly to less testing over the Lunar New Year holiday that began Thursday of last week.

A series of infections at factories and hospitals in the wider Seoul area have caused concerns of a potential virus resurgence, especially after social distancing rules were eased for small shops on Monday.

Authorities warned of a potential virus resurgence tied to holiday traveling, saying they could tighten the restrictions if the number of new cases continues to increase.

"The number of patients has been rising as more people received testing (for COVID-19) after the Lunar New Year holiday," Sohn Young-rae, a senior health official, said in a briefing. "There is a growing risk of the third wave of pandemic of surging again, turning from a downward trend."

The KDCA said related agencies will closely monitor large workplaces where workers stay in closed and crowded environments, as well as factories that accommodate foreign employees in dormitories, to prevent group infections.

Officials said about 1,000 workplaces deemed to be vulnerable to virus will be inspected, as well as unregistered religious facilities, warning of possible fines for those who violate regulations.

The health ministry is mulling to revise the current distancing scheme in a more sustainable mode by simplifying its five-tier virus curbs and easing the ban on multi-use facilities to mitigate its impact on small business owners.

The new rule will limit the number of people for gatherings depending on the level of new cases to give more flexibility in business operations, while mandating heavier punishments for those who violate regulations, the ministry said.

While the government earlier planned to adopt the new measures as early as next month, it will decide on the schedule depending on the outbreaks over the next two weeks

Currently, the Seoul metropolitan area, home to half of the nation's 52 million population, is under Level 2 distancing -- the third highest in a five-tier system -- and other areas are at Level 1.5.

The adjustment allows restaurants, coffee shops, gyms, nightclubs and bars in Seoul and the surrounding Gyeonggi Province to remain open for an hour longer until 10 p.m.

Earlier in the day, health authorities and related agencies carried out a final government-wide mock drill for the planned transport of AstraZeneca's vaccines ahead of the beginning of the inoculation program on Feb. 26.

The rehearsal focused on transporting AstraZeneca's vaccines from SK Bioscience Co.'s factory in Andong, 270 kilometers southeast of Seoul, to a distribution center in Icheon, 80 kilometers south of the capital, and then to 25 local health centers across the nation, the defense ministry said.

Of the 533 locally transmitted cases, 177 cases were reported in Seoul and 182 in the surrounding Gyeonggi Province. Incheon, 40 km west of Seoul, had 37 new cases.

A plastics factory in Namyangju, some 20 kilometers east of Seoul, has reported 130 cases among its workers, mostly foreigners living in the company's dormitory. More cases tied to the factory could be identified as testing of people who came into contact with the patients is still underway.

Soonchunhyang University Hospital in central Seoul reported 31 more cases to raise the total to 171.

A boiler factory in Asan, about 100 kilometers south of Seoul, added 25 new cases to have a total of 160.

The KDCA said 28 cases were from abroad, with seven from the United States, six from Indonesia and three from Japan.

The number of seriously or critically ill COVID-19 patients was 153, down eight from the previous day.

The total number of people released from quarantine after making full recoveries was 76,513, up 617 from a day earlier. (Yonhap)