The move came after one trainee had close contact with a virus patient in the southeastern city of Daegu, the epicentre of an outbreak in South Korea.

A surge in confirmed cases linked to a local church in Daegu this week sparked fears of wider transmission.

The 800 include 280 trainees, who have not yet started working on production lines, and accounts for a fraction of its workforce of 18,000 people in Incheon, a spokeswoman said.

SK Hynix, the world's No.2 memory chipmaker which counts Apple Inc and Huawei among its customers, said another trainee also had symptoms of pneumonia but tested negative for the virus. The trainee will undergo a second test.

SK Hynix has closed its training centre and hospital in Icheon, southeast of Seoul.

(Reporting by Hyunjoo Jin; Editing by Kim Coghill and Himani Sarkar)