South Korea's new COVID-19 cases hit almost 60,000 on Thursday, rising from a week earlier, as the looming winter virus wave adds to worries over yet another spike in transmissions.

The country reported 59,089 new COVID-19 infections, including 55 from overseas, bringing the total caseload to 26,784,142, the Korea Disease Control and Prevention Agency (KDCA) said.

Thursday's count is down from 70,324 cases the previous day but up by about 3,600 compared with a week ago.

Fifty-nine more deaths from COVID-19 were reported, raising the death toll to 30,223.

The number of critically ill patients stood at 437, down 40 from the previous day.

Health authorities have urged people to get booster shots to prevent infections before the winter wave takes hold.

The minimum interval period for booster shots has been eased to 90 days from 120 days for adults.