NIIGATA, Japan (Kyodo) -- The South Korean government on Friday held a memorial ceremony on Sado Island in Japan's Niigata Prefecture to honor Koreans who were forced to work at a gold and silver mine there during World War II, according to the country's foreign ministry.

The event, attended by 11 family members of deceased workers and South Korean Ambassador to Japan Lee Hyuk, was held independently by Seoul for the second consecutive year, the ministry said in a press release. Japan held its own memorial on Sept. 13 for all the people who worked at the site.

South Korea has demanded that Japan clearly recognize the forced nature of wartime labor involving Koreans at the site, while Japan, which colonized Korea from 1910 to 1945, has argued that such mobilization did not constitute forced labor under international treaties.

During his address at the ceremony, Lee said Friday's event was held to remember the many Korean laborers who were brought to Sado Island against their will and forced to work under severe conditions, while expressing deep condolences to the bereaved families, according to South Korea's foreign ministry.

The ministry also said in its press release that after the ceremony the families visited the site of the former dormitory for Korean workers, where last year's memorial had taken place, to lay flowers.

The mine complex was added to UNESCO's World Heritage list in July last year following a last-minute agreement from South Korea, which had initially opposed the listing.