After boycotting one organised by Tokyo, South Korea held its own memorial event on Monday for compatriots forced to work in a Japanese mine during World War Two, highlighting lingering sensitivities between the countries.

SADO, Japan (AP) — South Korea paid tribute to wartime Korean forced laborers at Japan’s Sado Island Gold Mines in a memorial ceremony on Monday, a day after boycotting a similar event organized by Japan, as tensions over historical atrocities continue to impact relations between the two sides.

Efforts by South Korea and Japan to hold a joint memorial service near Japa’s Sado Island Gold Mines, where Koreans were forced to work during Japan’s colonial rule, fell apart on Nov. 24 due to disagreements between both governments.

Japan will hold a memorial ceremony near the Sado Island Gold Mines, which were listed this summer as a UNESCO World Heritage site after the country moved past years of disputes with South Korea and reluctantly acknowledged the dark side of their history.

A memorial service for Korean laborers forcibly mobilized to the Sado mines, which Japan had promised to hold annually following the site’s inscription as a UNESCO World Cultural Heritage last summer,

The Korean government held its own ceremony on Monday to honor Korean wartime forced laborers at their former lodgings near Japan’s Sado Mine, following Seoul’s decision to boycott a Japan-hosted memorial held on Sunday.