The record 13,012 cases for the previous 24-hour period came just a day after the tally first topped 8000 despite the extension of tough social distancing rules.
The highly contagious but less-lethal Omicron became the dominant variant in South Korea last week, and the daily numbers could more than double or surge to even higher levels in the coming weeks, health officials warn.
"Going forward, our top priority is to reduce critically ill patients and deaths," Prime Minister Kim Boo-kyum told an inter-ministry meeting on Wednesday.
The government introduced a new testing policy in four designated cities on a pilot basis, under which only priority groups take a PCR test while others can get a rapid antigen test at a local clinic for faster initial diagnosis.
The program will be scaled up from Saturday to enable state-run testing stations nationwide to distribute the rapid antigen self-test kits. Another 430 local clinics will be added next week.
As part of efforts to free up resources for serious patients, the government has also cut mandatory isolation for people who have been vaccinated but tested positive to seven days from 10, and expanded self-treatment at home for asymptomatic and mild cases.
The Omicron surge has fuelled worries about a new wave of infections ahead of the Lunar New Year holiday that begins on Saturday, when tens of millions travel nationwide to meet families.
On Tuesday, some 46 South Korean athletes and coaches who will compete in the Beijing Olympics had to receive a COVID-19 test after attending a ceremony for the delegation where an official at the Korean Sport & Olympic Committee later tested positive.
South Korea has largely been successful in mitigating COVID, with 762,983 total infections and 6620 deaths.
More than 95 per cent of adults are fully vaccinated and 58 per cent have received a booster dose.
