South Korea's new coronavirus cases stayed above 7,000 for the second consecutive day Thursday and the number of critically ill patients hit an all time-high amid waning immunity and colder weather.

The country confirmed 7,102 new COVID-19 infections, raising the total caseload to 496,584, according to the Korea Disease Control and Prevention Agency (KDCA).

The daily tally was slightly down from a daily record-high of 7,175 reported a day earlier, the KDCA said.

The number of critically ill COVID-19 patients jumped to a record high of 857, up from a previous daily high of 840 reported a day earlier, putting further strain on the country's already overwhelmed health care system.

The death toll rose 57 on Thursday to 4,077, the authorities said.

The government reimposed stricter restrictions and implemented the "vaccine pass" on Monday to limit indoor gatherings and encourage more vaccinations in order to contain a surge in infections and the spread of the newly-emerging omicron variant. The measures will remain in effect until Jan. 2.

The authorities forecast the tightened measures to show effects starting later this week. (Yonhap)