South Korea's new coronavirus cases fell below 7,000 for the second consecutive day Sunday, but critical cases hit an all-time high again, deepening concerns over medical capacity amid the continued spread of the new omicron variant.

The country added 6,689 new COVID-19 infections, raising the total caseload to 517,271, according to the Korea Disease Control and Prevention Agency (KDCA).

Daily infections soared to a record high of 7,174 cases on Wednesday and remained above 7,000 for the following two days.

Sunday's figure marked a decline from 6,977 the previous day, but it is the largest ever daily caseload for any Sunday since the pandemic began last year.

Daily cases have stayed in the quadruple digits since July 7 amid growing cluster infections.

The number of critically ill COVID-19 patients reached an all-time high of 894, according to the KDCA. Critical cases rose to over 400 earlier this month for the first time since end-August and have remained at a high level.

The country added 43 more deaths from COVID-19, bringing the death toll to 4,253. The fatality rate stood at 0.82 percent.

The KDCA has confirmed 15 more omicron cases, raising the total to 90.

Starting Sunday, the government cut the dosage interval between primary vaccination and booster shots to three months from the previous 4-5 months to stem the spread of the virus and better protect senior citizens and other vulnerable groups.

A total of 42.96 million people, or 83.7 percent of the country's population, have received their first shots of COVID-19 vaccines as of Sunday, and 41.69 million people, or 81.2 percent, have been fully vaccinated, with 12.4 percent having gotten their booster shots, the KDCA said.

The government also plans to begin running visiting vaccination services at schools on Monday to have more adolescents get inoculated.

The so-called vaccine pass system will be applied to more business facilities, including restaurants, cafes, cram schools and internet cafes, starting on Monday after a weeklong grade period.

Only fully vaccinated individuals or those with a negative COVID-19 test result can visit those facilities, and any violation will lead to fines for both users or facility owners.

It is part of the government's stricter social distancing rules, which began to be enforced last week to be in place until Jan. 2. Private gatherings are limited to six people in the greater Seoul area and eight in the rest of the country. (Yonhap)