South Korea reported its first death from the new coronavirus on Thursday, while the mayor of Daegu urged his 2.5 million people to refrain from going outside as viral infections, linked to a church congregation, spiked.

A worker and vehicle spray disinfectant and water as a precaution against the new coronavirus in front of the statue of King Sejong in the Joseon Dynasty, at the Gwanghwamun Plaza in Seoul AP

The death of a previously confirmed patient in South Korea marked the world's ninth virus fatality outside mainland China. Other deaths have occurred in Hong Kong, Japan, Taiwan, the Philippines and France.

The Korea Centers for Disease Control and Prevention said the South Korean man, believed to be around 63 years old, died at a hospital on Wednesday and posthumously tested positive for the virus. It said authorities were investigating the exact cause of his death.

The centre confirmed 22 additional cases of the virus, raising the total in South Korea to 104.

People suspected of being infected with the new coronavirus wait to receive tests at a medical center in Daegu, South Korea AP

Earlier on Thursday, the mayor of the city of Daegu urged its 2.5 million people to stay home and wear masks even indoors if possible, after the southeastern city and its nearby towns reported 35 additional cases of infection with the new coronavirus. The 35 cases didn't include the additional 22 that were reported later that day.

In a nationally televised news conference, Mayor Kwon Young-jin expressed fears that the rising infections in the region will soon overwhelm the city's health infrastructure, and called for urgent help from the central government in Seoul.

“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,” Kwon said.

The Korea Centers for Disease Control and Prevention said 28 of those 35 new patients went to church services attended by a previously confirmed virus patient, or contacted her at other places inside a Daegu church. That patient is a South Korean woman in her early 60s who has no recent record of overseas travel, according to centre officials. She tested positive for the virus on Tuesday, becoming the 31st case in South Korea.

On Wednesday morning, Daegu confirmed 13 cases and 11 of them either went to the same church with the woman patient, or contacted her at a hospital, according to the disease control centre.

The Shincheonji Church of Jesus, which claims it has about 200,000 followers in the country, said it has closed all of its 74 churches around the nation and told followers to instead watch its online worship services on YouTube.

It said in a statement that health officials were disinfecting its church in Daegu, which the woman patient went to. They found this information while tracing her contacts. That Daegu church has about 8,000 followers. According to the church 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 coming to her Daegu church because she didn't travel overseas, church officials said.

“We think it's deeply regrettable ... for causing concerns to the local community,” the statement said.

The explosion of infections in Daegu and the neighbouring southeast region, 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 in the country.

Mayor Kwon spoke shortly before South Korea's government for the first time acknowledged that the country was beginning to see a “community transmission” of the illness, albeit at a “limited range.”

“We are seeing infections in some areas like Seoul and Daegu where it's difficult to confirm the cause or routes of the infections,” Kim Gang-lip, South Korea's vice health minister, said in a briefing.

“Our judgment is that (COVID-19) which has been introduced from abroad is beginning to spread through community transmissions in limited ranges,” he said, adding that the government would need to change its quarantine strategy that has been focused on tracing contacts.

In a telephone conversation with Kwon later Thursday, President Moon Jae-in said the central government will make all assistance available to help Daegu fight against the virus' further spread, according to the presidential Blue House.