China joined forces with South Korea Thursday as it denounced Japan's bid to list as UNESCO World Heritage sites some of its wartime industrial facilities linked to Korean slave labor.

Japan has been stepping up efforts to gain world heritage status for the 23 industrial facilities, where tens of thousands of Korean people were brought to such coal mines before and during the Japanese colonial rule of the Korean Peninsula.

"The Chinese side shares the strong concerns of the South Korean side with regard to Japan's application for the World Heritage," China's foreign ministry spokeswoman Hua Chunying told reporters during a regular press briefing.

"The Chinese side opposes Japan's relevant application and we urge Japan to face up to and properly deal with relevant concerns," Hua said. "We also believe that the World Heritage Committee will properly deal with the relevant issue in a responsible manner."

South Korea has expressed concerns about the Japanese bid, urging Japan to fully disclose the Japanese mobilization of Korean forced laborers before and during the colonial era. (Yonhap)