The tourists, all men, are from two counties in northwestern China's Shaanxi province and its capital city of Xi'an, China's state-run Xinhua News Agency reported. Their names were not reported.
The men left China Dec. 28 from the port city of Dalian and arrived in Inchon, South Korea, Dec. 29, Yonhap News Agency reported Thursday. The tourists were reported missing Dec. 30 after staying the night at a hotel in Inchon, Xinhua reported Sunday.
The Shaanxi Tourism Bureau said Saturday the tourists had not registered with local tourism authorities.
The Shaanxi provincial public security department was investigating their disappearance, Xinhua said.