The Korea Centres for Disease Control and Prevention did not immediately provide details of the death, but authorities earlier said the country had confirmed a total of 82 cases of the Covid-19 virus.
The death was reported as the mayor of Daegu asked all citizens to stay indoors and pleaded for help from the central government.
Kwon Young-jin made the request in a televised news conference after the south-eastern city and nearby towns reported 35 additional cases of infection with Covid-19 on Thursday.
Mr Kwon also asked Daegu citizens to wear masks even indoors if possible. He expressed fears that the rising infections will soon overwhelm the city’s health infrastructure and called for urgent help from the central government in Seoul.
The Korea Centres for Disease Control and Prevention said 28 of the 35 new patients went to church services attended by a previously confirmed virus patient. That patient is a South Korean woman in her early 60s who has no recent record of overseas travel, according to centre officials.
On Wednesday, the city confirmed 13 cases and 11 either went to the same church with the woman or were in contact with her in hospital, according to the disease control centre.
The Shincheonji Church of Jesus, which claims it has about 200,000 followers in South Korea, said it has closed all its 74 churches around the nation and told followers to watch its services on YouTube.
It said in a statement that health officials were disinfecting its church in Daegu, which the woman patient went to, while tracing her contacts. The Daegu church has about 8,000 followers.
According to the statement, church officials had been advising followers since late January to stay at home if they had recently travelled overseas or were experiencing even mild cold-like symptoms, but the 31st patient assumed she was having a common cold and kept going to the Daegu church because she did not travel overseas.
The explosion of infections in Daegu and the south east, as well as some new cases in the Seoul metropolitan area where the sources of infections were unclear, have raised concern that health authorities are losing track of the virus as it spreads more broadly.
“National quarantine efforts that are currently focused on blocking the inflow of the virus (from China) and stemming its spread are inadequate for preventing the illness from circulating in local communities,” Mr Kwon said.
In a telephone conversation with Mr Kwon, President Moon Jae-in said the central government will make all assistance available to help Daegu fight the virus’s spread, according to the presidential Blue House.