The Mayor of a South Korean city at the centre of a new coronavirus outbreak has told residents to stay indoors as a surge in confirmed cases raised the prospect of wider transmission.

Malls, restaurants and streets in Daegu, the country's fourth largest city with a population of 2.5 million, were largely empty in scenes that local social media users likened to a disaster movie.

"We are in an unprecedented crisis," Daegu Mayor Kwon Young-jin said at a briefing, as he warned of likely further cases.

One person has died and 104 people are infected in South Korea - the majority of which are in Daegu. 

The outbreak has been traced to an infected person who attended a local church, a scenario that KCDC described as a "super-spreading event".

Kwon cautioned that at least 90 more of the around 1000 other people who attended services at the controversial Temple of the Tabernacle of the Testimony, often labelled a cult, were also showing symptoms.

"We plan to test all believers of that church and have asked them to stay at home isolated from their families," Kwon said.

South Korea's Vice Health Minister Kim Kang-lip said at a separate briefing in the administrative city of Sejong that the situation was "very grave."

The cases previously reported in South Korea had mostly involved people who had travelled individually to China or come in contact with somebody who had.

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Daegu authorities ordered the shutdown of all kindergartens, while schools considered postponing the beginning of the spring semester scheduled for early March.

The Defence Ministry banned troops stationed in Daegu from leaving their barracks and receiving guests. The US military imposed similar restrictions on its army base in the city, which houses thousands of troops, family members and civilian employees.

Topics such as "Daegu lockdown" and "Daegu church" were among the top searches on major South Korean portal Naver as debate heated up online about whether the city should be sealed off from the rest of the country.

A KCDC official said the government was not yet considering that measure.

The church at the centre of the outbreak is a branch of the Shincheonji Church of Jesus, a religious movement founded in 1984 by South Korean Lee Man-hee who has about 500,000 followers.

The virus is spreading across the world, with new cases reported in the Middle East. 

Iranian health officials have urged all religious gatherings to be suspended in Qom, after two more people tested positive for the virus, bringing the total confirmed cases to five. 

Iran's health ministry says three more patients have tested positive for the coronavirus in the country. Two Iranians died in hospital after testing positive in Qom, the head of the city's University of Medical Sciences said on Wednesday.

"Two people have tested positive for COVID-19 in Qom and one person in Arak, bringing the total of confirmed cases to five in Iran," Health Ministry spokesperson Kianush Jahanpur said in a tweet.

Jahanpur said all patients were Iranian and the person in the central city of Arak was a doctor from Qom, the semi-official news agency ISNA reported.

Jahanpur said health officials had called for the suspension of all religious gatherings in Qom, a Shi'ite Muslim holy city about 120km south of the capital Tehran, according to ISNA.

Reuters