The visitors landed at Muan Airport, 385 kilometers south of Seoul, on a chartered flight last Monday, but 13 did not show up to board their return flight on Sunday, Yonhap News Agency quoted the ministry as saying.
International flights to Muan Airport resumed in July last year after a gap of two years due to Covid. The Thai charter flight was the first since the pandemic.
In October last year, 100 Vietnamese also went missing after entering through the Yangyang International Airport in South Korea as tourists.