Japanese officials’ plans to put several mines, shipyards and factories from World War II onto UNESCO’s World Heritage list have been placed under scrutiny, after South Korea said the sites were used to force Koreans into slave labour.

The row between the two nations focuses on whether they qualify solely for their role in the 19th century rise of Japan or whether the period where Koreans were forced to labour – between 1910 and the end of World War II – is a factor.

Korea’s UNESCO ambassador, Choi Jong-moon, was seeking to reach an understanding for Japan’s bid to grant 23 Japanese industrial sites UNESCO World Heritage status. In seven of these sites, Korea says 60,000 of its people were forced to work for no pay.

In a statement, Korea’s Foreign Ministry said that Jong-moon had returned empty-handed from a trip to Tokyo intended to get the seven sites removed from the listing, a notion rejected by Japan. At the most notorious of the seven sites, Hashima Island near Nagasaki, 600 Koreans worked in coal mines, with many dying from exposure or overwork.

“Our target is different in terms of historical background,” said Koji Hagihara, an official in Japan’s cabinet secretariat. “The Korean side has suffered in the war. That is a sad thing. That is why they are not happy about our nomination.”

Korea says that World Heritage “means the full history of a site should be reflected”. One compromise, the Koreans suggest, would be to mention the record of forced labour in official Unesco site inscriptions. But Japan refused the suggestion, with Shinji Takami, deputy director adding: “We don’t say it’s forced labour. There is some distance in our understanding.”