South Korea's new coronavirus cases fell below 5,000 for the first time in three days Monday as the country reimposed toughened social distancing rules amid concerns over the spread of the omicron variant.

The country added 4,325 new COVID-19 infections, raising the total caseload to 477,358, according to the Korea Disease Control and Prevention Agency (KDCA).

Daily infections soared to a record high of 5,352 cases on Saturday before falling to 5,127 on Sunday. On Monday, the government began four-week stricter social distancing rules to contain the rapid spread of the coronavirus and the omicron variant.

Under the new measures, which will remain effective until Jan. 2, private gatherings are limited to six people in the greater Seoul area and eight in the rest of the country.

More business facilities now need to require visitors to be fully vaccinated or to show a negative COVID-19 test result. Newly added to the so-called vaccine pass system include restaurants, coffee shops, cram schools and internet cafes.

The KDCA has confirmed 24 omicron cases, up 12 from a day earlier.

The number of critically ill patients came to 727 on Monday, down 17 from a day ago, while the death toll rose 41 to 3,893.

On the vaccination front, 83.1 percent of the country's 52 million population have at least received one shot of the vaccine, while 80.5 percent have received two shots. (Yonhap)