People carrying umbrellas stand in line for COVID-19 tests at a makeshift testing station at Seoul Plaza in central Seoul on Sunday, as the country has experienced a new virus wave. (Yonhap)

South Korea's new COVID-19 cases fell below 50,000 on Monday on fewer virus tests during the weekend, but the number of seriously ill patients reached a two-month high amid a virus resurgence fueled by a highly contagious omicron subvariant.

The country added 44,689 new COVID-19 infections, including 436 from overseas, bringing the total caseload to 19,820,739, the Korea Disease Control and Prevention Agency (KDCA) said.

Monday's figure sharply fell from the previous day's 73,589 due mainly to fewer tests but is still larger than the 35,860 cases logged a week earlier, as the country has seen a resurgence of the virus, triggered by the spread of the omicron subvariant BA.5, the most transmissible variant yet of the coronavirus.

The growth in new infections led to the surge in the number of seriously ill patients.

The country reported 287 critical cases Monday, the highest figure after May 18, when the tally stood at 313.

The KDCA reported 21 deaths from COVID-19, raising the death toll to 25,068. (Yonhap)