A large number of the country's patients are linked to a 61-year-old woman who is a member of the Daegu branch of the Shincheonji Church of Jesus, an entity often accused of being a cult.
The woman first developed a fever on Feb 10 but reportedly twice refused to be tested for the coronavirus on the grounds that she had not recently travelled abroad, and attended at least four services before being diagnosed.
The woman is also believed to have contaminated another person at a hospital.
The spike in new cases has prompted authorities to warn of possible further cases and asked Daegu citizens to stay indoors.
Daegu is South Korea's fourth-largest city, with a population of 2.5 million.
Shincheonji claims that its founder Lee Man-hee has donned the mantle of Jesus Christ and will take 144,000 people with him to Heaven, body and soul, on the Day of Judgement.