A Christian missionary society has been ordered or advised to conduct coronavirus tests for people at all of its affiliated schools and facilities in South Korea, government officials said Wednesday, as a cluster of COVID-19 infections tied to a subsidiary school has so far infected more than 320.

According to the Central Disaster Management Headquarters, a government agency, the number of infected people in the latest virus cluster traced to the International English Mission (IEM) School in the central city of Daejeon, an unauthorized school run by local Christian missionary society International Mission (IM), rose to 323 at six facilities.

The government agency said it had conducted on-site inspections at 40 IM-related schools and facilities and ordered or advised the society to carry out COVID-19 tests for all people at 32 facilities.

The missionary society reportedly runs 23 educational facilities with 841 students and teaching staff in 11 metropolitan cities and provinces nationwide.

"Preemptive coronavirus tests will be administered to all groups and facilities related to IM. There haven't yet been reports of IM-related people refusing to take the test," Yoon Tae-ho, a senior health official at the agency, said.

"A thorough epidemiological investigation has been under way, and all people exposed to infected students and instructors have been subject to the coronavirus test in cooperation with local governments," he said, vowing all-out efforts to stem the spread of the cluster.

The number of infections tied to the IEM School and the Missionary Training School, also in Daejeon, increased by five to 176 on Wednesday, while another IM-affiliated school in Gwangju, the TCS Ace International School, has reported 113 infections.

Most of the infections are among students and instructors.

Health officials in Gwangju said as many as 11 students shared a single dormitory room at the TCS school, fueling virus transmissions.

They have also confirmed that a total of 123 TSC school students simultaneously attended a class in the same place for two to three days last week in violation of the current social distancing guidelines banning gatherings of five or more people.

In another worrisome development, some infected teachers of the TSC school were found to have taught at several church-run kindergartens in Gwangju, raising fears of further community transmissions.

Authorities speculate that the infected people may have been exposed to the virus for a sustained period, considering that the incidence rate of early confirmed patients reached 80.7 percent.

They asked that anyone who has recently visited any of the IM-related facilities and organizations across the country immediately take a coronavirus test.

Notably, 39 IEM School students and teachers, who attended a winter retreat at a church in Hongcheon, 100 kilometers southeast of Seoul, from Jan. 16-25, have tested positive for COVID-19, heightening fears of virus transmissions among residents of the quiet Gangwon Province town.

According to officials in Seoul, the IM missionary society has four facilities -- two educational facilities and two research centers -- in the capital and one research staff member recently tested positive for the coronavirus. (Yonhap)