Most of the new cases were linked to an outbreak at a number of Seoul nightclubs and bars, many of them catering to members of the LGBTQ+ community.
That has raised complications for officials desperately trying to track those who might be infected in a nation where open homosexuality is often taboo and LGBTQ+ people still face discrimination, including job loss and hate speech.
Authorities have tested 4,000 people who had patronised the night spots in the Itaewon neighbourhood, but were still trying to track down around 3,000 more.
"Our top priority is to minimise the spread of the infections in the greater Seoul area," Prime Minister Chung Sye-kyun told a meeting with government officials on Monday.
Mr Chung called for local governments to work with police to track down the missing patrons, some of whom authorities suspect of intentionally avoiding being tested.
"We should quickly find and test them, and speed is key," Mr Chung said.
The outbreak has highlighted the potential unintended side effects of South Korea's invasive tracing and wide public disclosure of some patient information as part of its approach to tackling the coronavirus.
Health Ministry official Yoon Tae-ho acknowledged concerns that individuals within the LGBTQ+ community could be outed against their will or face discrimination if they came forward.
"We release the movement of confirmed patients to encourage anyone who might be exposed get tested voluntarily," he told a briefing.
"We urge you to refrain from distributing patients' personal information or groundless rumours, which not only hurts them but can also be subject to punishment."
The Health Ministry said 79 people have tested positive in connection with the Itaewon outbreak.
Seoul mayor Park Won-soon pleaded with clubgoers to be tested, promising personal information would be protected and warning that people caught evading testing could be fined.
The spike in cases comes as the government was easing social distancing restrictions and moving to fully reopen schools and businesses.
Seoul's education superintendent proposed delaying reopening schools scheduled to begin on Wednesday by one week in light of the new outbreak, Yonhap news agency reported.
In a speech to the nation on Sunday, President Moon Jae-in warned that "it's not over until it's over," adding that the new cluster shows the virus can spread widely at any time.
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